What would be better is if you could play 3DS games on the TV with your Wii U, that would be awesome!
Very, very unfortunately I do not think Nintendo would do this. They are still set in the 1990s mentality, look at their online gameplay/multiplayer functionality.Until they get some SERIOUS rollover of upper management, with fresh minds, I don't see it happening. It would be great, but so would a pokemon MMO game - people have been saying it for YEARS but Nintendo doesn't listen or refuses to embrace it.
I'm gonna hold a level of positivity in mind about this. As it is with the Gamepad for the Wii U, how they incorporate the Vita into PS4 functionality will be important. They have the capacity to do something amazing that blows anything the Wii U does to that point.
Given that they are technically two separate devices that can operate on their own, they are definitely capable to do something that even the Wii U can't. It would be interesting to see if they can actively pursue this avenue.
So you know how some games on the Wii U do not have the off screen capability? It's different than the Wii U GamePad because every single PS4 will be playable directly on the PS Vita - with exception to motion controlled/pseye games. As in, I can take the next Gran Turismo into my bathroom/bedroom and play it on my PS Vita if I wanted, regardless of distance to the PS4 itself since it does it over WiFi. The Wii U GamePad has a much shorter range because you're communicating with the Wii U directly, so it's about 30 feet open-range. My wifi goes over a hundred feet easily, I have an ASUS Dark Knight RT-N66U router.. arguably the best ranged wireless router ever made.
I also agree with you and I imagine Sony could also do more with the Vita, beyond making it a second screen as well. In fact, if you check the PS4 page, they already list iOS and Android devices as being able to be second screens for the PS4. So your iPad or my Nook HD+ can become second screens. It even says you can watch the game being played on your console via an app.. that's amazing innovation right there. Of course, I'd prefer the PS Vita as a second screen/controller over a tablet/phone because it actually has joysticks and physical buttons - something tablets/phones will never be able to replace.