I have a feeling Japan would be emboldened by victory over the USSR and try to take most if not all of Siberia east of Lake Baikal. That would be a big help to Nazi Germany during Barbarossa in my opinion.
The usual question is 'why does Japan want Siberia?'.
It's literally... Siberia. A place second only to the Sahara in terms of pop-culture references to barren wastelands.
Second, this would not really help the Nazis, as the 'far eastern troops come to save the day' myth is just that - a myth. New reinforcements did arrive, but they were from the Urals and Central Asian bits of Russia, not Siberia. The Soviets' Far Eastern Armies stayed largely in the Far East for most of WWII.
Basically, imagine you're invading the US east coast and someone parachutes a load of soldiers into the Nevada desert. You're probably grateful for the effort, but if they can't advance much further than that you'd almost rather they hadn't bothered.
And all this is moot, because the Japanese armed forces were not in any fit state to open another massive land front, given that they were at the time trying to annex large sections of the third biggest country in the world.