"I'll grant you that it's highly unlikely to happen, but I don't think system power is a huge concern when talking about a 2D platforming game. The engine issue is more of a concern, but I highly doubt that any current system would have problems unless the game was a horrible unoptimized mess."
Or we can simplify matters by referencing this paragraph THAT WAS ON THE KICKSTARTER PAGE:
"WHAT ABOUT NINTENDO?
Our budget left us with two options: Build the biggest, most beautiful game we can, or make sure it runs everywhere from the start. As things stand today, we can't afford to create the two separate versions of this game that would be necessary to make it run on every console. That said, we've heard legends about a remarkable treasure hidden in the castle basement..."
There, they're not leaving it out of the realm of possibility. You can't make SIX ENTRIES in the series on Nintendo handhelds and not pay the guys some kinda lip service. Plus considering how UE4 has an Android version, I doubt it'd cost THAT much to modify it to run on the Wii U.