Source
Basically, they released news about Japanese tanks at the Tokyo Game Show, where Girls und Panzer producer Sugiyama Kiyomi and seiyuu Fuchigami Mai (Nishizumi Miho) also participated. Aside from an introduction trailer and the tree, it was stated that offical Girls und Panzer voice mod packs will be released for free download, starting with Nishizumi Miho.
Side commentary: Tree is outdated.