I think allot of the competition will follow what the wii has done. What the Wii has done is quite incredible. It has been cheep enough for allot of people to own right from the word go. It has a large library of easy games that cater for a audience that just did not exist ten years ago out side the sims or mine sweeper.
I can quite safely say the big boys in town are here to stay for another round. Sony, Microsoft, and Nintendo.
Nintendo will be first on the scene with what I dub project "No more Fanboy". Nintendo will have their stock standard games for their new machine, which have probably already been developed by now and are just waiting to be ported to their new hardware. Flash based memory will have become quite cheap, and in a fight against piracy Nintendo returns to Cartridges that also add functionally to games, by adding hardware like printers, cameras, and microphones eta. power wise, it will probably have the same as the current PS3, but by then, will be nothing.
Microsoft will probably not call their next console the xbox 720 rather something stupid like "xbox xenon" or "master chief xbox". Microsoft will probably use blue ray, and their xbox live service for games, in a sense you can get Halo 4 on disk, or download it. It will also take advantage of motion sensing tech, but will keep the controller in much the same way it has been. Their next platform will be sightly underpowered to keep costs down. There will be no halo 4
Sony will probably be last on the scene with a larger more powerful than ever, but cheaper machine than the PS3 on launch, they will have learned nothing from the PS3 and will probably make their own format again to replace blue ray. It will be called the PS4, because sony have the perfect plan when it comes to naming consoles.
Sega Will not be participating, much to what people think
The PC crowd will be more jaded than ever. They still think they are the master race of gamers, and refuse to consider the fact that a joypad can be used to play First Person Shooters. They will endlessly mock the fact that no other gaming machine is more powerful than their own. Most will be playing World of Warcraft.
All up I don't think games can get any bigger. It already takes teams of three hundred people to make a game, or in the wiis case about eighty. I think we have hit a brick wall in terms of graphics, in a sense we will get better looking games, but nobody will care. Game developers will have to work on gameplay, or die. Though this could be an issue as we could see another video games crash, and I'll blame EA on that one.