We'll see the first two parts of a three story arc during the hour premiere: Water War and Gungan Attack. As confirmed at The Clone Wars panel at Comic-Con, we'll be seeing Captain Ackbar.
Along with the premiere date news, Lucasfilm released a new trailer for the season. The new tagline is Battle Lines. I'm hoping that means more time on the action side of war and less time on the political topics. The trailer definitely makes it seem that way. We've seen some of these clips before, but the last minute or so is all new. It seems that Anakin is falling further towards his dark path. At its heart, I think Star Wars is about the story of Anakin Skywalker and I'm looking forward to seeing more of his struggles in the upcoming season.
Can I also just say: this series is visually impressive. I wish I could watch it in a movie theater every week.