Marty "marty" Stratton of id Software has announced that a large update to QuakeLive will take place on Tuesday 14th. It will be down for 3-4 hours from early evening European time (late morning US time). Once down for maintenance, progress updates can be found on their Twitter page.

Following this update, any further modifications will be scheduled to be carried out on Tuesdays to create a sense of routine (excluding emergency updates).

Source: Quake Live forum