ImpElite, if you look on IGN and Gamespot when they are reviewing the expansion they both mention that the ending hints at a very likely expansion. And if you've played the game you'd know that too seeing as from what everyone is saying about how it ended...
All I Can Do Is Be Me, Whoever That Is. - Dillain
Every Song Ends, But Is That Any Reason Not To Enjoy The Music?
"Bow Chicka Bow Wow" - Tucker, RvB