Nintendo, Sony and Msoft will certainly be around. They build the hardware and I don't see any type of 'platform merger' in the works other than I'd predict Ps3 and 360 go full bore pursuing a similar motion system a la the Wii than the Wii chasing HD graphics.
Publishers only? EA, Activision/Blizzard probably are still here in their forms. THQ is certainly ripe for purchase. Ubisoft? I say they'll be around and pick up someone else along the way like THQ, Y2K, etc.
Then, and you can mark it down, Disney and Warner Bros Interactive. They're both wanting to be players and they have deeper pockets than everyone I just listed. They're around too.