IMHO, "Good Luck Charlie" is one of the best Disney Channel Original Series (Maybe it is the best Disney Channel Original Series). It was July 2010 when the series was renewed for a second season after about 11-12 episodes were aired (Plus a DCOM). 15 episodes of the second season has aired and so far no talk about a third season. Could the second season be the show's last? Will the movie close all storylines for the series? The show gets 3-4 million viewers for each episode (two episodes got around 2 million only!). "Shake It Up", another Disney Channel Original Series, gets about 4 million viewers for each episode.
Also, Disney Channel's been airing new episodes very quickly (I think this was due to some plan to boost their ranking in shows or something?) of many series. Disney Channel seems to be airing all Season 2 episodes quickly and then the Movie will come out later this year. If they pick up a third season, they would air episodes a little slower to save time for production.
This is just my opinion. I mentioned, GLC is one of the best Disney Channel Original Series in a long time. I would hate to see it end after 2 seasons, because it deserves at least one more season.