GameSpot's reporting the name change, which will, I'd imagine, mean that we'll see even more expansion packs for the game in the future. I just hope they're reasonably priced ;)

"Valve Software has revealed to GameSpot that Aftermath, the upcoming expansion pack to the award-winning 2004 shooter Half-Life 2, has been renamed 'Half-Life 2: Episode One.' When asked whether the name change is indicative of a change in direction for the Half-Life 2 franchise, Valve marketing director Doug Lombardi replied, 'episodic.'"