Yeah I was going to post something along the lines of what Squinty said but go distracted reading another thread.
I do that a lot.
Basically yeah, our max capacity flexes and grows as we gain/lose people. At first there was just the seven or so of us, which got the KotS game off the ground to give people a good example PbP D&D game and meanwhile it was all just forum posting games and such. Then a mafia game started and pulled more people down here, and a few wandered over from the 'mothership' and saw that the only D&D game was full, so AA started his own campaign and got it up and going while Squinty saw how things were run and decided to get a Pathfinder game going and pulled in some new blood...but then we sorta stalled for a bit again. The between the 5e game starting, the DoP games moving down here, a second mafia game recruiting, and finaly DS's game recruiting we expanded yet again and hit the point of separating the Forum games from the PbP. Afterwhich talking to Rstnme in the RPG boards led to him wandering down here and starting up a game.
We're near capacity given our current population, but if a few of the players so desired we could easily support another game or some caliber. Especially of the shorter and easier variety. And more importantly, short and easy games with low player counts that appeal to users from other parts of the boards will draw them down here and hopefully they'd see the D&D games and such and want to sign up for something or run their own game.
Another aspect, which is a little more far reaching...and something that I'm working on from a total community aspect, bringing more traffic to the site will obviously give us a bigger exposure and pool of users to find players in. So I've been trying to keep active discussions and informative threads in the RPG sections to help throw us up on the google searches when RPG players search for things. Its why I'm working on the Ranger handbook and why I try to fish up articles and such when I can.