"Peace" which in reality would be more of an extended ceasefire, would have a huge benefit for USSR..
1. Time to get all factories moved past Ural working at top efficiency and get quality control issues resolved
2. Time replace losses an retrain the Air Force. In Kharkiv VVS got absolutely annihilated, even a year will make a massive difference
3. Time to reorganize and retrain, all the division that at this point are running on what is left of the officer corps that has been annihilated in purges and then bled dry in 1941
This is not a gamble this is a gift from Goering or whoever.
When summer of 1943 comes.. USSR will have a far stronger military machine and Stalin can make a decision as to what to do. As added benefit this separate peace just force Allies into a much more active war vs Germany. USSR and Stalin were incredibly frustrated with lack of direct combat help. Well now they can have their payback.
They most likely get disappointed in TTL as well. The Wallies simply weren't ready in 1942, both the logistics and geography were against them. Where exactly could they attack the Nazis outside of North Africa? They try invading France in 1942 they get stomped to the curb with little effect on the Nazis. The UK might agree with the US to go after Japan more while the US builds up forces as France is complete suicide and even North Africa much tougher when the Luftwaffe sends its planes southward.