Ecco DC has the best looking 2D sections I've seen in a game, and still no one has done anything serious with that.
I don't think it's dead, but it depends on the audience you consider. It would be very, very hard to get mainstreamers to take a 2D platty seriously. I don't consider the existence of rehashed 2D platformers only on handhelds to really be all that "alive". I want to see a real, playable, interesting and surprising platformer on a full console, stretching every limit that could viably work in a 2D platformer. I think it can be done, but only because of, basically, Sonic and NiGHTS. They have 2D gameplay that isn't just about the next obstacle, and that's the kind of gameplay that needs to be considered, imo. If that's not making sense, think of Rez. Similar idea of it being about the play.