I'm cool with that, but the main issue is finding enough people interested -- same deal with Battlefield: Bad Company 2. There just aren't enough people with the game who are willing to turn up on Fridays. If there were a ton of regular participants, we'd have the flexibility of playing different games as there would always been people to fill the slots, but that isn't the case.
So far, we have approximately a dozen regulars (people who turn up at least once a month or more, many of them every week). We've been sticking with L4D2, occasionally TF2 and recently added Section 8: Prejudice as a handful of us bought it. We really want to add more games, but considering the limited participation, you could say we're between a rock and a hard place.
By adding BC2 or BF2 we might gain a few interested participants, but many (most, in fact) of the existing regulars would be alienated. TF2 and L4D2 are currently the only titles that most of the TS Steam group currently own and are interested in playing. The immediate solution, of course, is to find another game everyone owns/wants to play, and I believe BF3 will offer that.
I'll have to speak with Julio, but I'd like to run a BF3 launch giveaway. Until then, I'm open to suggestions on promoting the Friday Night Fragfests. For a while, I ran a front page notice every Friday night with mild success. The ultimate goal is to create a group of 50+ gamers participating regularly. At that point, we'd have far less restrictions on the titles we could play.