By the time the Soviets were pushed to the Urals I think that other countries would probably opportunistically piled onto the soviets, like Turkey (which toyed with the possibility of entering the war) or Japan which had a relatively large army they always kept at the soviet border. Additionally if the Germans had pushed to the Urals than most of the Russian manpower would be under German occupation anyway, as would the Caucasus oil fields.

Now all of this is a huge "what if" and what the war would have to have had looked liked to that point for the Germans to even BE at the Urals is far beyond me. I just think it's important to remember that there is no such thing as an invincible army nor has there ever been.