Of course while Hitler was beating the Russians back to the Stone Age, the Wehrmacht would have still been taking a beating itself. By the time Adolph was shaking hands with Tojo at the Manchurian border his army would have been severely weakened. Additionally, Adolph would then have the problem of controlling a huge land area with millions of inhabitants that demonstrated pretty good Partisan ability.
THAT would be time for the Brits and French to strike, assuming they had had the sense to rearm in the interim. But they were pretty stupid in that respect.