One approach to the one console standard, but multiple manufacturers, is to go the 3DO route and that didn't prove viable. The other approach to one console is to have one maker so dominant, that they don't think of anyone else. If you see what happened with Nintendo from NES to SNES, or Sony with the PS3, you see why that isn't good. In the case of Nintendo, they ended up mangling Mortal Kombat. In the case of Sony, they had the PS3 launching at an insane price point. Does one think the PS3 would be priced where it is now, if Microsoft wasn't around to cause Sony to feel what last place is like? You would likely looking at $400 MINIMUM for a console, if there was no 360 about.
All and all, one console strategy isn't going to happen. Companies will be too greedy to end up having this happen. Someone else will enter. And as for being able to play everyone anywhere, well, the locking people into a network where they have to own a console, is what is banked on. Sony, while not charging for online play, is banking on people just playing others over the PS3. And "Only on X" is still a viable strategy as far as gaming goes. Apple also employs this to. I don't see them, anytime soon, opening up their iPhone technology to multiple manufacturers.
Flat out, you want to have this dream? The closest one gets is a PC.
