The matter is a lot more simple than most people here assume.
Videogame market is business and business is just about money. Nothing more.
Companies won´t jump their productions on a console if they can´t be sure that its install base can, at least, provide realistic chances of matching their sales predictions and give them the profit they want.
It doesn´t have nothing to do with technology. Companies can work out these technical matters just fine. Activision, Disney, Tt Games, Ubisoft, Namco don´t seem to have faced big problems porting their PS3/360 games to the WiiU so far, despite minor features.
The WiiU currently faces the same problem Vita faces: it doesn´t have many 3rd-party games because the install base is small and increases in a slow pace. Smaller install base = smaller sales opportunities for 3rd parties.
So much that both PS4 and XboxOne, despite having good launch line-ups, currently don´t have much for the future - despite enhanced versions of games already scheduled for their previous generations. Companies will wait to see how sales go before jumping on new projects, exactely what they´re doing right now with the WiiU.
