Microsoft did recently re-announce their next OS.. GDC would be perfect to show that off for PC devs. I doubt that M$ will be showing off that much. E3 is stil where 90% of all announcements will be made like usual. Major announcements will be during their press conference.
Valve, will show off early demos of their new engine.
Nvidia, will show off the 9800GTS, and 9800 GTX.
Havok will have their new engine shown off.
Sony, will just show trailers and maybe have a few demos of games just to update people on progress. Major announcements will be during their press conference anyways. Will release new and improved dev tools.
Nintendo's Major announcements will be during their press conference.
AMD, who cares..
Intel - QX9770!!!
Epic - UE4










