Well, I’ve often thought of that. First and foremost is going to be cosmetic DLC. Different outfits and equipment, in a perfect scenario enough people would play the game that major brands would want to sponsor some of their own gear into the game. Also tournaments, I want to have in depth leagues, teams, stats and championships. I want to hold big events maybe each quarter (perhaps the winners of different leagues will compete for a championship). Hopefully it’s accessible enough to transcend the current e-sports demographic and start getting some more people into twitch and MLG etc… This is all still an idea at this stage though so don’t hold me to anything.
I also have tossed around the idea of other game modes. Like you I love capture the flag and control points in what would otherwise normally just be another first person shooter. The first thing that comes to mind is a dodge ball game mode, where you can explode (or implode?) the opponent with the protoball!
My idea is to keep developing and building on it. Keep making DLC/Cosmetic stuff, and other game modes to help keep it fresh and most importantly fun.