There was an article in the Times a month or so before the end in Germany where the last B17 to roll off the assembly lines was displayed next to a new B29. Willow Run is going to cease production of B24s on June 28.
No reason to deploy bombers that are no longer in production is probably the thought here, and flying only one type of bomber in combat makes the logistics and maintenance easier.
Considering the training time delays for converting -17 & -24 crews to the -29, that is exactly the decision one would expect from someone who knows the A-bomb will preempt everything.
From all the little things going on it looks like the US Military is figuring on at least one more year to knock out Japan.
Ha Ha little did they know!
Regards
alfa6 ;>}