id Software have just announced they've started working on a new Doom game. From their website:

Production has begun on DOOM 4™, the next journey into the legendary DOOM universe. We are expanding our internal team and are currently hiring to work on this highly anticipated title.

"DOOM is part of the id Software DNA and demands the greatest talent and brightest minds in the industry to bring the next installment of our flagship franchise to Earth," said Todd Hollenshead, CEO, id Software. "It's critical for id Software to have the best creative minds in-house to develop games that meet the standards synonymous with our titles."

DOOM 4 will join the award-winning series which has consistently topped sales charts throughout the world.

I'd assume we'd see releases on Windows, Xbox 360 and PlayStation 3.