The big question for me is if consoles and handhelds can maintain current big three / big two model.
My guess is Sony will drop the handheld so Nintendo will be fine in that space. Nintendo might then make a hybrid system next, a handheld that can use an add on to play on your television leaving Microsoft and Sony to battle for traditional console space.
The gaming market now is so much bigger than twenty years ago that I could see various type of gaming being supported world wide. I mean arcades still soldier on in Japan even though been dead in the west for over a decade now.