The Russians have always been pretty fatalistic about that shit, though. You know you've got it bad when you're better off under the Mongols. Germany didn't enter into WWII over reparations, Germany entered into WWII because WWI was a stalemate rather than a loss and they had unfinished business to attend to. I'm unaware of any unfinished business in Europe other than Cyprus. Chile and Argentina had all sorts of miserable debt problems and nobody invaded anybody else. I'll bet Japan throws the first punch. They're likely to see their standard of living continue to decline. The one problem they have is a lack of able-bodied men capable of marching...
Maybe Putin decides rebuilding the USSR is a good idea? War usually means someone wants to conquer some territory, and there doesn't seem like anyone else in Europe that would be interested in expansion. Actually, I'd bet on China taking a few islands. They do have an army, and feel like they owe it to Japan. There's a solid WWIII: Russia decides to rebuild the USSR, and China takes Taiwan and invades some of Japan. Not likely.
I'm sure he'd love to have Ukraine. I'm sure he'd love to have Kazakhstan. Most of the rest of it is a net drain. If anything, Kazakhstan might be a flashpoint; the chinese have been investing heavily in Kazakhstan and if Russia decided they wanted it back, things might get exciting.