It'd be hard for the Red Army to create such an encirclement, but it ain't completely off the table. AG South is practically nonexistent by the end of this. Yes, they can evacuate via Crimea, but they can't evacuate everyone & can't take heavy equipment either. The Third Battle of Kharkov was a failure for the Soviets precisely due to the forces retreating from the Caucasus coming and stopping them. But if they're all dead or POW, there aren't enough German or really any Axis forces in Ukraine to stop the Soviets from cutting off Ukraine from the Axis. So the Soviets completely cuts off almost all German/Axis forces in Ukraine, killing whatever was left of AG South. So by the Spring of 1943, Ukraine is Soviet again. It's doubtful if Germany can even do the Battle of Kursk, as they have no ready forces. Also, to compensate for AG South being brutally killed, they would most likely strip forces from AG North, weakening their position and allowing the Soviets to push them out from Leningrad, ending the Siege & potentially encircling portions of AG North. Hell, maybe the USSR can even encircle the Rzhev Salient, because the Germans are taking troops from there to other fronts. After having their troops encircled in the Leningrad-Novgorod Area, the Rzhev & Center Front, Ukraine, AND the Caucasus, the war dramatically shortens, and the Soviets can potentially advance all the way to the Rhine.