I think pretty much everybody agrees that for the time being the Crimea is lost to Ukraine. But history proves, as also pointed out by Clausewitz, that stranger things have often happened and the situation might well change in the future.

There is in my opinion little doubt that for the West Russians center of gravity is it's economy, while for Russia it is the Westerns political willpower. Interestingly the EU+USA are roughly twenty times bigger in GDP terms the Russia, almost the same factor by which the Ukraine mainland dwarfs it's occupied territory. It would certainly be the supreme irony if Russias Crimean robbery would result in the long term loss of the Ukraine.

A lot of other questions arise for other countries in the EU/NATO and CIS. For example will we see an increase in military spending in Europe? Will Sweden and Finnland maybe join NATO? How will the Belorussian strongman react?