I think it'll be a little of all of the above. I don't think PC gaming will be going anywhere, but at the same time PC gaming is likely shifting primarily to MMORPG type games where there's a monthly service fee. RTS games are also likely never going to leave the PC until someone goes to all the effort of reworking the control scheme for the likes of Kinect and Move.
Consoles will still be around for the more immersive single player games, like JRPGs. Handheld consoles will still tend to appeal to people who are looking for a bit more of an immersive experience than you find on cell phone/tablets.
Finally, tablets and phones will be the realm of the quick pick-up and play game that you might be able to play for 5-10 minutes here and there. Basically an Angry Birds kind of game. No real plot to speak of, simplistic gameplay, and you can pick it up and put it down on a whim.