From what I understand, using 3D models is much more efficient than making good sprites, so 3D models would be the way to go. The problem is that, apparently, publishers don't believe that a 2D game will sell in the modern day. And to be honest, I don't see NSMBWii changing that calculation anytime soon. I think 2D Mega Man is going to stay on downloadable channels, at least for this generation. I also don't think they have what it takes to pull off half the things you're calling for.
It'd be awesome if I was wrong though.







