Except to fit a Blu-ray disc, it will be quite bigger than Switch, that system also look like it lacks some buttons

See the problem with my imagination is that my background and experience is constantly filtering out terrible ideas like a handheld that uses blu-ray discs.

First off, that's a gamecube using tiny game cube discs, looks like something Ben Heck made, and is in no way official. Second, it's about 2 inches thick and looks incredibly uncomfortable to use for more than 10 minutes. That is if it's actually a real thing and not a 3D render for some art school project.

Quick question, do you remember using a Discman? Remember anti-skip? Remember how annoying it was when your song skipped? Try doing that on a blu ray which is many times more dense, and much more sensitive to motion, and if your game "skips" chances are the whole thing crashes because PS4 games weren't designed with anti-skip technology in mind. Nevermind the size and weight it would actually add to the unit.

There is a 0% chance that any Sony held made based off of the PS4 contains a blu-ray drive.

You don't need me to prove the tech is exist on the market. Just read the progress of tech on the Internet , use your logic here, Switch is the prove and PS4 is the prove and AMD 7 nm is in the horizon. SONY has the screen tech, the batteries tech, the controller tech. As far as my concern PS4 Portable is not a rocket science, and not beyond people imagination. 

Every gaming market are connected on one line , which is gaming. And then there are other to be considered, Console gamer, Portable gamer, and both.  And also casual and hardcore. You can pick all of the line whatever you like it's share the same market "GAMING". Of course focusing on one connecting line like Casual or Hardcore has the benefit. But Switch has prove it the other way around or even if it's not prove the other way around, they are still making a lot of revenue. 

What i am saying untaped market are the hybrid Market and dedicated market  that only Nintendo rulez alone. 

PSP market exist not because of games, but because they released PSP on the market and followed by the games. PSP  was created because  portable market already exist created by  Nintendo .  PS Vita also created because of the demand of powerful portable on the market. It doesn't matter if they play the same games or not.  Switch also exist because it has Zelda and other cross gen games or even port games. Why the Vita is failed it's not because they are lack of exclusives  but because a lot of thing, if i mention one by one will take new thread to make. 

I am not saying Marketing research for PS5 are the same with PS4 Portable. They are totally different but in every Marketing research they always have a general research about what consumer want from PS device and what are the consumer though about the competitor like Switch and Xbox. And in Japan i believe (i don't need to prove ) people would prefer to buy Switch over PlayStation. Hell even Vita out sold Nintendo Wii U LOL.  Around the world maybe 50% consoles and 50% portable, but PS4 portable is the hybrid consoles for the 50% portable market and 50% console market. 

Well we can assume the market exist because we are not being serious here LOL. But my prediction are based on SONY habit on releasing product and Switch success in the market. Also gaming trend and tech improvement around the world. Honestly nobody knows what SONY want and what will they release in the future but i can assure u , they will not created something new , they will created something that already exist on the market , something like VR,  AR, Cloud gaming, or Portable/hybrid product in the market. 

you on some otherworldly shit

Just going to interject here.
Because... The burden of proof lays with the person who makes the claim.

So if you assert something is true, then you need to back it up.

And that works for the opposition as well, if they assert that something isn't true, they need to back their statements up.

The Switch is not representative of what is possible with a hypothetical Playstation 4 mobile device.

For starters... The Switch isn't using the latest and greatest display, battery technology, GPU, CPU, Ram technology to begin with even on it's release, progress certainly hasn't stood still.

I am not saying i am agree with the OP  timeline. It can be in a year or two years after PS5 release  or at the same time as PS5 release date or  maybe in the middle of PS5 life times. The tech   need to mature first and  the chip die size and other factor. need to be considered. But it will not take a long time to get the point where Horizon will be playable in portable mode like Zelda was. Remember how Switch able to preform better performance then Wii U in portable mode in less then 6 years. And PS4 portable just need to match or slightly match PS4 . 

I am not deluded my self , Switch are sold because of Zelda a cross gen title, hell  multi platform titles that available on Wii U as well. And also many PS4 users tend to have multiple PS4 at their house. And also Indies are sold a lot in Switch more then in steam.  If SONY releasing PS4 portable or even PSP 2 , why not? It doesn't means it has to come out in near future, i am just assuming Switch Success might intrigue some of SONY investor and management to try again. 

One of reason why Vita failed is because they couldn't supported two platforms in same time, I dont think that changed and that will see Sony portable any time soon.

They did during the PS3 and PSP era though. However, the reason the Vita failed was because handhelds were becoming less and less relevant in the west and it was too expensive. The lack of third parties and the success of the PS4 didn’t help either.

And Nintendo did with Wii and DS, but they failed with with Wii U and 3DS, I talking that its far more dificult to support two difrent platforms in current gen. You can bet that if Sony had bigger focus on Vita with stronger 1st party and early price cut that Vita would done better than it did, but Sony had PS4 on horizon and they didnt want to focus too much on Vita, for instance 3DS also didnt had great start but Nintendo made huge price cut and start pumping strong 1st party games.

Agree. Games are more complex and have longer development cycles these days so supporting 2 platforms isn’t feasible anymore.