OK, why would the Japanese wait? They're running out of oil and they don't have compromise built into their mindset. The only way I could see this playing out was if the Japanese secured oil supplies from Soviet Russia in a kind of Eastern Molotov Agreement. It is valuable to the Soviets as it ensures they can bring troops from Manchuria to fight the invading Germans, and also because any Japanese threat is mainly to the USSR's long-term ideological enemies, the colonial powers and the USA. With oil supplies secured by Soviet Russia, the Japanese could continue their conquest of China, which would take a good few years, then review the status of the West. If the Allies have finished Germany by then, Japan can agree a peace with China under her thumb. Would a war-weary Britain want to go to war with Japan over China? Unlikely. And if Roosevelt has died, would Truman pursue the same policy against China given the Allies now face a Soviet occupation of half of Europe which Roosevelt had unintentionally made happen?