There is an update to the story though that there is currently no sequel in progress:
Update 2: Hirooka, a publicity staff member for the Girls und Panzer anime, posted on the anime's official blog that there are currently no plans for a sequel. Hirooka specifically described the newspaper report as "mistaken information" and apologized for the confusion among fans.
He added, "Of course, the possibility [of a sequel] is not zero, but first, the entire staff is working our hardest on the broadcast of episode 11 and 12. We ask for your continued support."
Things are leaning towards Ooarai somehow winning the national championship. After this it would be difficult to come up with a sequel to meet the expectations set by the first season. Things could be expanded to a worldwide Sensha-do tournament involving other countries. However part of the appeal was also seeing various tank models that are not as well known in action as well as the more well known models. The same appeal wouldn't be there if World War II tanks pop up again but could be remedied if the teams start using the next generation of tanks, say Cold War era. As much as I too would like to see a sequel, I would be happy if one does come out but not crushed if one doesn't.
Personally I like the show because of an interest in military, primarily World War II matters. And even if you don't, the tank driving is quite impressive for girls that don't even have their driver's license yet.