It was revealed today that there will be a Call of Duty: Black Ops Double XP Weekend, next weekend. This begins Friday, November 26th and will last till the end of the day on Sunday, November 28th.
Update: Treyarch basically ended up canceling the Double XP weekend, it was never fully announced by them but was by Microsoft for the Gold Weekend. It has been moved to another unknown date. It will be coming, among more to come sometime after that over the next year.