Mark Rein of Epic Games, when talking about Unreal Engine 4 and the Wii U, has said:
…I don’t think it’s our intention to bring Unreal Engine 4 to Wii U, but Unreal Engine 4 is going to be supremely scalable. We’ll run on mobile phones and on a wide variety of things, so if a customer decides they want to port an Unreal Engine 4 game to Wii U, they could. But Unreal Engine 3 is a really good fit for that platform.
And after all the teasing, that is a bummer.