What I'd imagine seeing is instead of really focusing on stand-alone devices, game consoles will become integrated into TVs themselves. It'll be like buying a Smart TV., just the main difference will be customers needing to choose whether they want PSN or Live integrated into the TV. There will still be a separate box for those with older TVs, but it'd be less and less needed to get. Needless to say with that train, this will make physical versions of games basically obsolete.
Of course, the biggest hurdle for that vision is the countries' internet infrastructure. With the size games are even now, there are massive download times, and people can easily hit their caps from a single game. And with net neutrality in danger, those downloads could be throttled even further.