I find this rumor very strange.
For starters, Unreal Engine 3 has been confirmed to run on the Wii U by developers. Secondly, it’s Metroid; it’s going to get a Wii U game. It may not be getting one any time soon, since Nintendo is probably going to be more hesitant about publishing a Metroid title after Metroid: Other M‘s reception (I think it actually stands a better chance at showing up on the 3DS before the Wii U). So it’s really not a big stretch of the imagination to say that Metroid Wii U will use Unreal Engine 3.
Whenever Metroid finally does comes to the Wii U, it’s very possible that it could run off an even better game engine. After all, we have no idea how long the franchise will be on the back-burner.
Whatever engine the game does ends up using, I’m sure Nintendo will make sure the game looks great. I mean come on, this is Metroid we’re talking about. They know it bridges the gap between core and hard-core titles. It’s the closest thing they have to the type of modern-day shooter that regularly appears on the the Xbox and Playstation 3; there are certain expectations for a game like that, and it not like they want the game to look bad.
However, there is a big part of this rumor that is most likely false: the part where a tech demo was shown somewhere, and this tech demo was apparently made by Epic Games in collaboration with Retro Studios
While we’ve had numerous hints that Retro Studios is working on something big right now, and we’ve guessed that it will probably be mentioned at E3 this year, there has been no indication that this mystery title is Metroid. Sure, Retro did create the Metroid Prime series, but that doesn’t mean they’re making Metroid Wii U. One could speculate that this may be why they are only helping Epic Games out with the project, but the whole thing sounds too good to be true.
I won’t complain if I’m wrong, but I also won’t deny that I’m hoping Retro is actually working on a new IP.