The way I see it is that the Japanese leadership was not at all likely to surrender, and without the atomic bomb the USA will be hitting the Imperial Japanese in an Allied version of Operation Citadel: the landing zones are known for both sides and they've both made extensive preparations for it. I do think in the event of such a scenario that the Soviets would have done a lot more in Manchuria, probably gained all of Sakhalin and started blitzing through Hokkaido at the same time as the USA's punching through the Kanto Plain.
One thing that's always been an interesting hypothetical is what would happen assuming the IJA tries banzai charges right into the Soviet army of 1945 where it had enough firepower and callousness about human life to make good sport out of that kind of tactics. I see absolutely no reason that banzai charges right at the Soviet military are going to work any better than they did at the US military. The USA at the time was quite peachy keen on Axis civilian deaths, and the Soviets after 4 brutal years of warfare against Nazi Germany are hardly inclined to fight and die any more than they have to. If anything the situation might well end up reversed, the US Army making headlong attacks without real sense to and the Soviets accepting surrenders of cities that allow for it, using firepower to annihilate any that refuse.
Your thoughts? In this case the A-Bomb would probably be available by 1946 and for a real nightmare might have been used by both sides in whatever happens in the Korean peninsula.