D&D Encounters Season 3 Keep on the Borderlands will be starting on Sept 22. It will be held every Wednesday until the end of this season. Currently one table per session is planned, with a couple of seats reserved for walk-ins.
Encounters on Mondays will finish up Season 2 of the Dark Sun campaign. It is currently unclear if Mondays will also host Season 3 of Encounters, but most likely not.