The A9X is probably more powerful than a Wii U, the Tegra X1 is almost certainly, neither are expensive chips.

People here really don't understand how powerful modern affordable mobile chips are.

The Vita is ancient, and that was only $250 almost five years ago.

The chip isn't what's expensive ... for a portable it's the LCD screen that's the no.1 cost ... if you're willing to accept a decent/low cost screen like a 1280x720 display at 6-6.5 inches that's easy enough to sell by this fall for $200-$250. 

This is the Tegra X1 versus a PS4 running an Unreal Engine 4 demo:

https://www.youtube.com/watch?v=9XzIZWO1qdg

Keep in mind the X1 footage is recorded off a projected screen so the colors look more washed out, but it does a decent job holding its own versus the Playstation 4, considering it runs at like 6-10 watts versus 130 watts for a PS4. I believe it's running this demo at 720p too ... scale it down to 540p and it could probably get even closer to the PS4 in details. 

This chip is *not* expensive either ... it's in the Shield console with 3GB of RAM for $199.99 ... and this console is sold at a large profit because Nvidia doesn't make money off game sales. And the console is already nearing a year old.

Nintendo could likely very easily have this type of chip in a portable with 3-4GB of RAM for $200-$250 come fall of this year. Then the home version could have even better graphics, but this would allow for a lot of scalable games and even portable ports of next-gen PS4/XB1 games ... this would be a game changer for Nintendo IMO. 

As you say yourself, Nintendo only has so much manpower, there is no point investing any significant portion of their workforce into games like Twilight Princess HD and Starfox Zero when Tantalus/Platinum can handle it. At this stage, resources are better spent making sure NX has the best possible chance of success, rather than shoring up a platform that will be lucky to pass 15 million in sales.

What's a dream is thinking they have any major unannounced titles for Wii U, despite not announcing any for over a year and a half.

Nintendo can't afford more big Wii U games if they want to really support the next handheld and next home console.
Had Nintendo had big Wii U games coming and E3 2015 would have looked like E3 2014... and it clearly wasn't. Far from it, actually.

For next gen, Nintendo really needs a sub-200$ handheld or things could result in another 3DS situation.

I think the 3DS price cut was an overreaction to be honest. $200 3DS sells perfectly fine (relative to market conditions), cheaper 3DS models have not improved sales whatsoever, and yeah it didn't sell a $250, but that's because it was a shit proposition for $250. It had no big games, a retread of Nintendogs, and while the 3D effect was OK, the graphics technology was underwhelming, like a souped up PSP.

People aren't going to buy a portable just because it's cheap, because nothing is cheaper than free (as in free games on tablets). And even a cheap Nintendo portable will get its legs cut off by even cheaper Android tablets with HD screens that are now getting as low as $99 or less. 

So IMO the challenge for Nintendo is to improve the experience of the portables they offer so much so that they are miles beyond a tablet and legitimately might even be able to function like a console. 

And before someone says Vita ... no not really ... the Vita can't even handle PS3 ports, let alone PS4. The mobile processing power back in 2011 just didn't exist for that, but in 2016 ... it's getting there. 

The only cheap model that sold like shit is the 2DS, and to be honest that device is kinda a piece of shit, it's a downgrade in every sense of the definition. It's the equivalent of Nintendo releasing the original Gameboy 2 years after Gameboy Color or releasing the original Gameboy Advance 2 years after the GBA SP. Ya, they would be cheaper but they would also be inferior and be seen as poor products, so it's hard to say if a lower price would help 3DS. Personally I think an actual price cut would have been more effective than the 2DS was but Nintendo is in a state of profits over user base so they didn't go that route.

I don't know if Nintendo overreacted. I think they "saw" what would happen  if they just cut the price a bit.
Having a big cut would impress and regain customers back. MK 7 and Mario 3D Land were also part of the plan to drive sales in the long term.

The new handheld shoud strive to not become another tablet device. Keep the handheld DNA and then throw in a bunch of stuff to make it a purchase worthwhile. The other way around would be a potentially mistake.

Remember when Iwata said NX would absorb Wii U's architecture?
Well, it seems it might happen after all, just not how most people thought:

http://www.neogaf.com/forum/showthread.php?t=1166717&page=18
https://www.reddit.com/r/NintendoNX/comments/3xuumg/rumor_nintendo_to_unveil_nx_in_january_at_ces/

Lots of speculation. But seeing as i don't speak that tech language, i don't know what's possible and what isn't.

How do i conclude 4 years for HAL? Because HD games aren't developed in one year without full engine and assets partially developed. The wii U game was obviously developed in paralel with the 3DS title or was a small title. Theres no 2 ways about it. Everyone knows these things. Its common knowledge. The likeliness (and i'm beeing extremely nice here) that you are wrong is extremely high because of that. Development cycles on HD titles are longer than SD titles because obviously they require more resources. This is a fact, not a guessing game. What you are doing is wishful thinking. I'm afraid that once we know the official info you will be sorely disappointed.

I don't see how i can be possibly be beeing ignorant by pointing you out on your completely unrealistic predictions and incomplete partial info.

That is not the point is it? Nintendo is developing said games cooperatively. They are surely working on NX software. But to think it will be ready for a next-gen home console for later this year, sorry to say, but its insanity.

Besides we do have confirmation that they are working on Wii U titles. Zelda U itself is more than confirmed and its probably the biggest title internally developed at Nintendo to date.