So the buzz on the net is that there will someday be a season 2 of Girls Und Panzer... maybe a few years from now...
No proof, but yeah... the movie is the best selling film by a huge margin in Japan right now, THIS WEEK. It has sold over 130,000 copies, the next film doesn't even come close... 7,000 something. The film also made over $20 million beating all anime records in Japan, the
previous record holder at about and the numbers still keep coming in.
Things are done differently in Japan, as the writers and creators have moved on to other projects for this year, but in Japan, they tend to jump around then come back to projects. Being that this series has outperformed all other animes out there, yes better then Naruto and Attack on Titan, it would be surprising to not see it continue.
They are making a spinoff manga too, and content is still being added all the time to their
official blogs and
Twitter. Hopefully you can read Japanese.