Who said UE4 wasn't on Wii U? Epic said they have not talked about any platform outside of PC so foremost, it wouldn't be official.
UE4 will not run on Wii U going on the leaked / rumoured specs imo.
A CPU that is rumoured to be on par, if not worse than the 360's 'Xenon', 2GB's of GDDR3 Ram and a barely 500 gigaFLOP GPU will not cut the mustard next gen im afraid, esp when it will be running another display on the controller which will again take resources away from what is being displayed on screen.
With those specs i doubt it will even get the latest UE3 games (Star Wars 1313) or the latest CE3 games (Far Cry 3, Crysis 3).
The Wii U is again aimed at mostly casual gamers no matter what Nintendo said at E3 2011, with a smattering of older / lower end cross platform games like Batman, ME3, Darksiders 2, AC 3 and Aliens.
If you are buying a Wii U expecting to play even 2013 current gen multiplatform games (GTA V, Tomb Raider, Bioshock: Infinite, Splinter Cell: Blacklist, Watch Dogs ect) never mind next gen multi platform games (2014 - 2020) then you are going to be really let down imo.
It will however be a great console for Nintendo exclusives and for the first time in HD, if they manage to look like the Zelda tech demo i will be more than happy with that.
If you want to enjoy the big name multi platform games both at the end of this gen and next gen aswell then i would advice buying a gaming PC or if you prefer one of the other consoles.