The idea of Germany rolling their tanks towards the Urals is really mind boggling. We have about 200 operational battle tanks left, not exactly a threat for anyone. And the German reunion was mind-boggling expansive. Probably in the range of 1-2 trillion dollars. There is certainly no incentive whatsoever to attack other states for territory.

If anything, in a far future some more eastern states might apply for EU membership, but with the current state of things even that isn't overly likely and would happen in an absolutely peaceful manner.