Epic want to focus on PC's first, they also like to push the visuals as far as they can go. And a system that is using a card that has been on the market for a while will not be able to use the initial release of the engine because its PC only. But I do believe someone at Epic said that it would eventually be on the WiiU since UE4 is made to be scalable. (Not going to look for the quote)
Most of the stuff about UE3 for the Wii U can be understood as this: They wanted to get their tools on the Wii U so they can get money on the system's games and get a mind set, since UE4 wouldn't be ready to get a game out in time for the launch of the system they ported UE3. This allows them to focus on getting the PC version of UE4 out fully. They are still not even liscening the engine openly yet on their site. Heck they are pushing UE3 for Windows 8 right now. (And they updated the platforms page to include the Wii U) Once that happens they will look to bring it to the other platforms they deal with. They did something like this with UE3
