The new patch will be implementing a number of features requested by the fans, and will make some changes to the gameplay. According to id, players of the game should expect a "faster, smoother and more highly competitive experience." id hopes this will please both veterans of the game and those who are only just discovering the title.
To be a bit more precise over what the update will include, you'll get a new game type, a new weapon, and several professionally made new maps. The update should also bring increased mobility and control, improved performance with ambient lighting, and weapon alterations to challenge competitive players.
The update is currently in a small private beta test, but the hope is that it'll be released publicly prior to QuakeCon on August 3. We presume this applies to the PC version only, with id making no announcement regarding the Xbox 360 version of the game.