As announced by developers, the upcoming version 9.17.1 comes with changes in the German, Japanese and American tech trees. Here are some details about what will happen to the German one:
UPDATE: info from Konstantin „Foton” Soldatov, WoT Publishing Producer, translated by Vladimir:
1. If the Maus was researched in the tech tree, after the split the new tier 10 has to be researched and bought.
2. If the Maus was researched, the new heavy tanks VK 100.01 P and Mäuschen will be unlocked.
3. If you only have the VK 45.02 B with XP on it, nothing changes. You keep the XP and can research the new tier 10. But the new Maus branch will be completely locked.
WoT PC Product Coordinator:
Good news for you is that once you research Maus before update, VK 100.01 P and Mauschen will be unlocked for you as well. Bad news is you need to hurry up.
Also some info about the new Stronkhold sistem:
Economy of Strongholds will be adjusted to match new settings. There will be no “defending” as we know it now. Battles for Stronghold will be replaced with a new game mode that requires more dedication and preparation than Skirmishes but pays off in faster development of your clan’s Stronghold: higher risk, higher reward. Industrial Resources will be still be used as currency for SH development.