Upvote:2
Axis forces predominantly stopped short of Moscow due to freezing temperatures. Russian reinforcements were used to counterattack and push them back (which, after amazing gains, collapsed in spectacular defeat).
The Japanese Empire was not a significant threat the the Soviet Union (despite Stalin's fears). Vladivostok could have been taken, and this would have been of some significance, but not game changing.
What was significant was that the Russian industry had been pulled back behind the Urals, making the prospect of enemy forces reaching it in 41/42 impossible.
Without the Siberian forces the Moscow siege would likely have continued in the following year. Whether the Germans could entirely envelop the city (much less capture) is another thing however. Even with the capital captured, it does not necessarily mean that the USSR would have fallen (though it makes it that more likely)