I think the option of doing psnow on phones wpuld be good. Maybe start of in xperia phones to test. But building new mobile hardware that has to last for 5 or 6 years seems like a expensive idea or at least very hard to start

I think you're missing the point of this post...

It's a mobile device backed by PlayStation.... A hybrid

The Vita doesn't need to be replaced, it needs to be fixed. 

1. Price Drops
First of all, the Vita and PSTV both need permanent price drops. The Vita needs to be no more than $130, and the PSTV needs to be $30 (stand-alone) and $70 (DS4 Controller Bundle). If nothing else, people buying new DS4 controllers could drop another $10 for a new console.

2. Hardware Revision: Vita
The Vita needs another revision. This revision should address all of the biggest complaints about the Vita;
-Use SD cards for storage and sell a Vita card adapter so people may still use the expensive cards they bought.
-Add additional shoulder buttons. OG Vita can still use the legacy touch controls, but new Vitas would benefit greatly for PSNow and Remote Play if they received R2/L2.
-Make the sticks clickable for R3/L3. Like with the previous point, legacy controls will let the OG Vitas handle and the new Vitas would have better PSNow and Remote Play control.
-Include AC wireless for better connection via Remote Play.
-Increased CPU/GPU to support PS2 classics.

3. Hardware Revision: PSTV
The PSTV needs is first hardware revision to be a big one;
-Use SD cards for storage and sell a Vita card adapter so people may still use the expensive cards they bought.
-Include AC wireless for better connection via Remote Play.
-Increased CPU/GPU to support PS2 classics.

4. Software: Applications
There are a number of rather important applications that BOTH Vita and PSTV need to support. The PSTV would see the most benefit from this, as it would become a viable set-top box. The following a necessities, but their inclusion could page the way for more niche programs.
-Netflix: Available on the Vita but not PSTV.
-Vudu: Not available on either platform, needs to change.
-Amazon Prime: Available on the Vita but not PSTV.
-PlayStation Vue: Not available on either platform, needs to change. Could be a real game change for the PSTV specifically.
-HBO GO: Not available on either platform, needs to change.
-The CW: Not available on either platform, needs to change.

5. Software: Classics
As previously stated, both platforms need access to PS2 Classics. This would encourage more releases for PS2 Classics. As a side, any PS2 Classics on PS3 that are also available with trophies on PS4 should be linked. Anyone who owns the PS3 versions should automatically receive the PS4 version as well, and the PS3 version should receive Trophy Support. Anyone who has purchased both already should receive a credit for $9.99 (the original cost of the PS3 versions of the Classics). The same would apply to any additional Ps1 Classics, such as FFVII. These versions would all also be playable on Vita/PSTV.

6. Software: New IPs
The lower development cost of the Vita and PSTV makes it the perfect testing ground for new IPs. A good example of this in action is Gravity Rush.

7. Software: Existing IPs
Sony should also invest in existing IPs for the Vita and PSTV. Some games can be remakes, some ports, and some spin-offs. Good picks for instant success include;
-God of War
-Uncharted
-Last of Us
-Gran Turismo
-Demon's Souls
-Bloodborne
-Patapon
-LocoRoco
-Ape Escape
-Ratchet & Clank
-Jak & Dexter
-Crash Bandicoot
-Sly Cooper
-Legend of Dragoon
-inFAMOUS

8. Bundling
PSTV should be, by default, bundled with every PS4. There should also be a $500 Pro/Vita bundle.

9. Branding
The differentiate between this "new Vita" and "new PSTV", they should receive new names. "Vita Pro" would stay in line with the naming scheme for the PS4; PSTV could utilize the much better name of "PlayStation TVita".

It would take more than a powerful system with a Sony logo on it to sell in the modern handheld market. The Vita is proof of this 

Either way mobile gaming doesn't appeal to me anymore.  The home experience is what I want. 

These are all great points, and I think this would have made Vita a lot more successful. Had Sony made these moves in 2013 or 2014, and never dropped support, then I think these adjustments would be right on the money. Now, however, I think it is to late to save Vita. They have to move on and build something around PS4 if they want to succeed.

The product line-up you layed out is on the money. I think a PS4 Super Slim with built in 512GB of storage and no disk drive can be profitable at $100 in 2020. This will basically take the place of the PSTV, but it will be done right because it will support all PS4 software, which at that time should include all PS1, PS2, PSP, PS Vita, and PS4 games, with inhancments and trophies for the older titles. With full support of banking apps, health/fitness apps, trading apps, shopping apps, video editing apps, photo apps, etc., etc. that will become available on the PS ecosystem, this device will do very well in the niche TV box market.

The Handheld unit adding SD support, L2/L3/R2/R3, while retaining the front and back touch will make playing all games identical on both home and mobile PS4 units. With the mobile unit running the same 7nm PS4 chipset as the new PS4 Super Slim, it will also have full access to all PlayStation Games, Apps, and Services. This will give it a library of 10's of thousands of apps day one, making it very competitve to iOS and Android from the very begining. It will also assure that every major Sony franchise is made for the device.

Now the most important thing missing. There has to be a phone model and a Handheld/Phone model. In todays market a mobile device has to have a connected option. Even if a handheld had Mario, Pokemon, Gran Turismo, Uncharted, Halo, and Gears of War, it would have a hard time getting to 50M in todays market, if it has no connected option. 4G is an absolute bare minimum. Making a Slab Phone, a Handheld/Phone, and a full dedicated handheld version would be the only way to make the platform big enough to stay viable. They have to have options for every user.

If Sony does everything right they should be ready to have this by 2020;

Home

-PS4 Pro+

-PS4 Pro Slim

-PS4 Super Slim

Virtual Reality

-PSVR Core

-PSVR Casual

Portable

-PS4 Pro Laptop

-PS4 Tablet

-PS4 Handheld

Mobile

-PS4 Slab Phone

-PS4 Phone/Handheld Hybrid

All of these devices would be built on the 7nm fabrication prosses. Every device would run the PS4 OS. Every device runs every piece of PS4 Software. All aspects are cloud supported by PSN, allowing a seamless experience between devices. 

By 2020 the PS4 ecosystem should be well over 150 Million units sold. With over 100M ative users daily. With the release of the PS Mobile line-up, that will jump to over 200 Million active users and over 400 Million devices sold by 2024. This will make PlayStation a major player in the home, potable, and mobile computing world, and make Sony highly, highly profitable.

All we need is for Kaz to unifiy the company behind one vision, and utilize all aspects of Sony to make great Sony devices. The days of running in house competition are coming to an end, and once the relience on other companies OS's is ended, they will coome out much more profitable, with a much more stable position. With the right moves Sony will be one of the most profitable companies in the world, and see massive stock gains. 

Who would buy it though? Those wanting to play PS games will buy the PS4. Why split the studios up? Sony does not have enough Studios alone to keep the next handheld afloat unless they start stealing from there PS4 user base. Nintendo have over 30-40+ Studios compared to Sony's 16 (Rough estimates). Like I said if this thing would sell Sony will have to create a bunch of studios to run there portable division ($$$) or start using there big PS4 Devs to swap between the two platforms. I am sure you would all rather ND develop a PS4 game than a Portable game right?

I don't see 3rd party support moving away from Nintendo in this area to move to Sony's next portable platform either. The problem with the Vita was its Price and lack of games, and unless Sony do the things above to support it than there might be a chance and than they need to drop the price to stay competitive because iPhone and Galaxies aren't going anywhere anytime soon.
So in other words, Sony needs to spend heaps and sell for a lot less. There not exactly swimming in money especially after the VR project which I see them pushing for many years.

Like *merman* mentioned above, why not just focus all there games on what's doing well than competing with a juggernaut and undefeated champion when it comes to portable devices. Probably not the best move to make right about now.

Just my thoughts.

Your right about one thing, right now is not a good time, but 3 or 4 years from now is the perfect time. 

Why? 

Because, at that time 7nm fabrication will allow Sony to create a handheld and phone around the original PS4 spec.

What is the significance of this?

Sony and 3rd parties will not have to do anything special, because all games made for PS4 will work on his device. It will be even simpler to support than the PS4 Pro.

Who would buy it?

How about the 240 million people that bought the PSP and DS when they were competitive with the best mobile devices on the market.

Why not focus on PS4?

Well for one thing if they when they shrink down the PS4 chips to 7nm, even with this device out, the focus will still be on the PS4 ecosystem. So they will still be focused on PS4, this will just be adding enormous value to all PS4 software. This is important, because, if they only focus on PS4 at home, then they will eventually loose massive ground to Microsoft, Nintendo, Apple, Amazon, Google, and many others that are looking at a bigger picture. 

Finally, on Sony needing a massive early investment. Well once again, that is exactly what the PS4 is. When they say all of your PS4 games are now available on this mobile device, that alone will sell a massive amount of units. Most importantly, by Sony owning the OS and the ecosystem, every dollar spent on the device will earn them some change, something that the current Xperia phones don't offer, and never will. Every way you look at this, it is the only way Sony builds a profitable, and prosperous future. They have to unify the company, and PlayStation is the only pure Sony product left. Theh have to unify around PlayStation as the OS and Network future of the company.

Nice assertion there. Completely ignoring the fact that back then what the psp could do was a novelty. There were no iphones or tablets and the device was unique in terms of watching movies/tv shows, music, and playing games.It even had skype which people could use to call their friends. You know what's also hackable? ouya. How much did that sell?

It's like saying that the only reason the wii was a success was because it was hacked. I mean why didn't the Wiiu sell well it was such a success? In other words, your argument is extremely weak. Especially claiming that it was the only thing that made it sell. The psvita didn't sell well for a number of reasons just like the psp sold well for a number of reasons, including how easy it was to hack it.

As for your second paragraph, you don't seem to understand the concept. It's supposed to be a phone. People are willing to spend up to $600 or more, unless they get a plan, which they could also do with what the OP described. The comparison with the Switch is completely invalid. The switch is a console. Not a phone.

Didn't sony already try this...and it failed miserably? A Playstation phone? The post suggested a device that is essentially a console but it has phone capabilities. People already have a phone, why'd they buy a device like this unless they're into playstation as a brand? If Nintendo made a phone, as much of a Nintendo fan I am, I wouldn't buy it. I already have a phone and I wouldn't drop some odd $600 bucks just for games. It just doesn't pan out. The issue here is, it's too expensive.