How would that work? A handheld for a reasonable cost is not going to come close to the Wii U's power, even if it was released in a year or two. I think the Vita is throwing you off.
Per pixel, I'd say the Vita is actually pretty similar to thr PS3 in terms of power. Maybe even a little better. That does not mean the Vita is even close to the PS3 with raw power. It's all about the Vita being 544p while PS3 games are usually 720p. On a handheld this doesn't matter that much, but compare vita.tv to ps3. In that apples to apples comparison PS3 games look a heck ton better.
Basically I'm saying Nintendo could make an affordable handheld that's visuals look like the Wii U's, but they couldn't make one cheap that actually runs Wii U software. If the hybrid console had tv out people would easily tell it was weaker than the Wii U.
Also, I think an increase in power is always great. GameCube's graphics were "good enough" at the time yet look how great those games look in dolphin. A 1080p SM3DW certainly wouldn't be a bad thing. You also can do tons of other things besides better graphics with increased power. Physics and ai have a ton of room for improvement.
Lastly, the big thing that worries me about a hybrid console is controls. The mobile factor limits it to a flat design like 3DS or Vita instead of being curvy like the gamepad or pro controller. Also many gimmicks are out the door. Waggle wouldn't work and asymetric games wouldn't work.
The thing I've thought would be cool would be a gamepad with a 2DS, or a 2DS with gamepad features. 2DS is only $129 which is not much more than the gamepad replacement. Selling a Wii UDS for $300 wouldn't break the bank.







