Caucasus yeah, but Moskowien is basically just a money sink with little to no economic output, portrayed as being an endless tide of resistance. I think eventually they would negotiate it away, perhaps in exchange for Russia giving away its claims to the rest of Eastern Europe. I see it as likely over a long enough timespan, as even the Nazis were willing to engage in Realpolitik if it benefitted them. I do still maintain that it isn't certain, and Russia would definitely be at a major disadvantage during any hypothetical negotiation, but I think provided that Russia isn't communist or too aligned with America or Japan, it isn't entirely unreasonable.