The East front was war to the knife. Stalin will not throw in the towel. Reaching Moscow and taking Moscow are two different things. The Germans even reaching Moscow in September is doubtful, and remember, taking Moscow will require the Germans to throw away their best asset, movement. Penetrating even the defenses of September will incur heavy losses. Couple this with the effects of attrition due to pushing their men and machines to the limit to reach Moscow at this time and you realize that the Germans will enter the city exhausted, out of gas, out of ammo, with 25% of their machines. House to house, factory to factory fighting against Molotov cocktail wielding Hero's of the Soviet Union will take a terrible toll on irreplacable men and machines. Stalin would not remain in a Moscow about to be surrounded, he would retreat forming legions with which to counter attack. Large sections of Moscow could not only hold out, but actively fight against the Germans, maybe until spring. Most likely a December or Janaury counter strike by siberian divisions and the remaining Red Army would most likely open the jaws of the German trap holding Moscow. The outcome of all this is that Moscow, not Stalingrad, is the rock that the Wehrmacht breaks on. Hitler wouldnt let anyone retreat from Moscow, forcing the same outcome as Stalingrad. Suffering 100-150,000 killed, wounded, and captured in the Moscow campaign, EASY, in just 3-4 months would destroy the Wehrmacht of late '41. Training camp graduation rates for the men and factory output for the machines was too low at this time to come close to replacing losses like these. So again, no matter how bad the Soviets would be hurt, the Germans would be hurt just as much, a viscious circle. Giving the Germans no larger advantage than they had. A Germany captures Moscow scenario most likely means that both sides are exhausted in early '42, most likely preventing the Germans from repeating their advances in the South as they did in history in '42. The lines would probably stay static as both sides attempted to recover, the Soviets receiving 100's of thousands of tons of lend lease goods through the year.
This most likely means Germany would have to strip Western Europe and Africa of troops to have a chance at a summer offensive. Operation Torch most likely conquers North Africa virtually unopposed, invasion of Sicily in '42? Italian invasion early '43?

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