There is a box in the Spotlight section of the USA Xbox 360 Dashboard, as the time of this post, where you can vote for one out of four games to be the July Deal of the Week. The winner's DLC will be 50% off in July
There's: Mass Effect2, Battlefield: Bad Company 2, Left 4 Dead 2 and Assassin's Creed 2. As a BF fan, I recommend voting for Bad Company 2. Even if you have all the DLC or perhaps don't have any MS Points or simply wouldn't buy the DLC regardless... vote for the game so everyone who is interested can get in on this deal.
The more people who buy the DLC in July, the more people will be playing the game, at least in theory. Good luck.