I doubt it too, we would have had many bombs by then. Many Japs dead from starvation, but not all, via blockade. Is the method of their death the deciding factor? More likely would have died than died via the bomb, along with the Allied POWs. Doesn't seem like a good trade. We kept the faith with our POWs by ending the war quickly. MacArthur would have had two extra pens at the surrender ceremony had we relied on the blockade though.
We would have had to fight two wars in Japan, the first against Tojo, the second against the Communists.