Activision have announced that Quake 4 has gone gold and that it will be in stores for October 18th (US).
The long awaited sequel to QUAKE II, QUAKE 4 enlists gamers in the role of Matthew Kane, a member of the Earth Defense Force's legendary Rhino Squad, to penetrate deep into the heart of the Strogg war machine and engage in a series of heroic missions to destroy the barbaric alien race. "On October 18, QUAKE is dialing it up to 4.0 on the Richter Scale with this new chapter in Earth's war against the Strogg," said Todd Hollenshead, CEO, id Software. "Fusing an epic war-story driven single player campaign, and fast-paced QUAKE III Arena inspired multiplayer, QUAKE 4 delivers a gaming experience fans will be raving about for years.
Taken directly from : Shacknews

EDIT : I was informed that the release date in the UK/Europe will be the 21st October.