Valve might (MIGHT) consider doing away with their episodic model for future titles. You may remember they instituted the plan for their series of Half-Life 2 expansions. You may also remember the first of these appearing in April 2006, with the second only scheduled to arrive later this year. Those are long waits for short games, and Gabe Newell says they'll be taking stock of your thoughts on the subject once Episode 3's done:
I think what we really want to do is have a couple of examples out there - Episode One, and how long it was to play and how long it took to develop, Episode Two, Portal and TF2 and then the third part of the trilogy; and then sit down with the community and say, 'OK, so what do you want?
I may as well jump the gun, get it off my chest now: six years between full games, I can do, I'm easily distracted, but long waits between 3-4 hour releases? No, thanks. Valve: Episodic game plan may not last [CVG]