Seriously... I don't say this as a hater but you seem so confident of what the Wii U can do... Wy is that? Like I will say I don't know I don't have a clue. But we're you there in the meeting room when Nintendo was developing the console. You are says g Wii U can handle everything ps4 can? Why can ports only reach it seems at best for the moment 720p 30fps. Like no even 720p 60fps. I'm just not as confident as you and 3dude.
There isn't any reason to downscale when the hardware to pull off all of the same graphical "tricks" is there. There may be some limitations API wise as Nintendo continue to revise their toolkit and developers get more experience with the platform. Other than that, barring any developers coding down for the Wii U simply because they aren't willing to put the effort into it (a la EPIC), multiplatform games will look largely identical on all three platforms. I've said this before, later in the gen we will see some developers do things that can't be done on the Wii U, but you would be hard pressed to notice them.
Keep in mind that OpenGL and DirectX on x86 is extremely common and any developers who have built games for PC in the last 10 years have gobs of experience with it. Even with all that experience and supposed power of the PS4, the best we've seen for the PS4 looks, well, a lot like what's coming out now for PS3 with some sharper textures.
Nintendo's platform is completely new, No one has ever seen or worked with this hardware before because the hardware itself never existed before Nintendo, IBM, and AMD built it. Not only does it take time for developers to wrap their heads around that, it takes time for Nintendo to develop, distribute, and cycle the API's and development environments to aid in development. What we saw in Killzone should be fairly indicative of what to expect from the game when it releases. It may look a little better or worse because they'll have final hardware and HDK/SDK, but they'll have to add much more into the game than one on level with limited physics and AI, and character animations, the list goes on.
We've also seen a glimpse of what early development on an open world game on Wii U looks like, and that video alone should be enough to prove that not only can Wii U pull off enormous worlds, but it can do it and put AAA games like Skyrim to shame.
We are at a point where even sizable gaps in performance amount to little visual gain, but offer gains in supporting areas of game development. The PS4 is sizeably more powerful than the Wii U, but it will translate to very little improvement in the overall look and feel of a game. It depends on the game itself, to be fair, but the hardware is there to do the same thing on both systems. Expect both to have absolutely stunning exclusives too.