According to the Left 4 Dead 2 blog, the development team is still alive. The L4D team aknowledges that it has been awhile since the last l4d2 update and that the next one should be out in a few weeks.
Some of the versus changes the team is currently working on include infected bots. This will surely help even out those games where team members rage quit. I wouldn't expect the infected bots to be anything less than perfect, seeing as how capable the human AI is...
Another change is the removal of the auto spawning in the finales. I truly welcome this change, as most are tired of being spawned far away with a boomer, just to be shot and killed making the long journey to spray potential victims.