An invasion of Japn though costly would never last into the 50's! It would take 5 years to capture Japan...i doubt it!
Though fighting would have been tough pockets would have been destroyed as they were on Okinawa. The fighting would have been on an Iwo Jima scale but once the country was split an enemy cannot fight very well without supplies comming in. After a few months starvation and disease would have become the big killer of the japanese populace.
the armies in China would have had even less supplies and would have been obliterated by the Russsians.
Once the country was divided which the allies prob would have done. Adequetly suppliying and running the government would have prooven impossible. Production of arms, food, and medicines would have been been extremely low after bombings and being captured. Then the amount that actually make it to the front would have been even less. The amount of time an organized army could fight in this condition (even a fanatical army) would have not been THAT long. I would guess about year total. And agree with estimates that the war would have been done with around 46-47.