I don't think the Soviets would have succeeded even if we're talking immediately after V-E day. Yes, it would have been an absolute blood bath for the western allies on the ground as the Soviet war machine was sweeping though europe. But if the west held on long enough, they certainly would have won. Here's why:

As early as June, B-29 XX and XXI Bombardment Commands were grouped under the newly-formed US Strategic Air Forces, Pacific, under the command of General Carl A. Spaatz. LeMay often boasted that if duty called, he could re-route "sizable" numbers of B-29s to Europe, as Boing had by now solved their earlier production delays and was pumping copies of the heavy bomber out quite healthily.
The Superfortress, augmenting B-17 and B-24 bomb groups (which by now could operate on the European continent) would sway the Soviet advance considerably. And I'm not even mentioning the A-bomb. Remember - it was the fire raids which caused more damage/casualties per city.......