Microsoft or Nintendo It's close.
Microsoft depending on the next year or so if they can manage to get profits after the price cut and if they maintain second place or not. If sales keep dropping even with price cuts I believe that will push them to release a console sooner - but I expect the 360 to be out another 2-3 years before their next system.
Nintendo because they could probably sell boat loads of the Wii HD - and it could probably be easily backwards with Wii games so the Wii would still be viable for years.
I think Sony won't because they seem pretty serious about the ten year plan - to regain profits and sell some of their systems. They've lost quite a bit of money on the PS3 and probably want to get that money back so I doubt they are even working on a PS4 right now.
It's just that simple.
