That said, there is some misconception's that just because an engine supports a platform, doesn't mean a game a developer makes for say high end PC's and PS4, will all of a suddon work on that other platform, even if it has "support". Case in point, just because IOS and Android are going to be supported in UE4, doesn't mean those platforms will get ports of those PC and PS4 games.
*edit* I should clarify, even though games use the same engine, developers can do with that engine what they wish, and some games will push more geometry, more effects, more particles, more physics, more scripts than other games, making porting to lesser platforms difficult/unfeasible. This becomes a real problem when these areas that the game pushes are critical to the games design (turning them down/off would compromise the vision).
Well first off, I want to establish that the auteurist idea of "vision" is bullshit. Developers compromise on vision a thousand times during development, and all things considered I'm not convinced the usable gap in power between the Wii U and whatever the PS4 and nextbox has to offer is significant enough that major, gamemaking features will have to be omitted. In fact, Wii U support means that the game is much more likely to have those features should it go to the Wii U since the engine makes code compatible across different hardware architecture. Will there be some games that use every bit of power of the PS4 or Durango? Bet your bottom dollar. But those games tend to be console exclusives and most likely not made on UE4. Coding to the metal makes for some fantastic gains, but it also makes the games MUCH harder to port. UE4 on the WiiU isn't about those games though, it's about the ease of transposition and the promise of positive support without expectations, aka, the majority of games. We focus on the outliers, we lose the meaning of the greater whole. Make sense?