I don't know if there's a clear cut answer or synopsis that anyone can agree on 100% with the nuking of Japan. Whoever uses a nuke in the future though, prepared to be demonized for a long time 
I am not a scholar, but all the amount of reading I made on the matter (and on strategic bombing in general) make a compelling case that the US rationale was pretty sound in military and political terms. Hiroshima debates, on GAF or anywhere else really, are filled with a ton of straight up misinformation or misunderstanding of the context of the war. The morality of it is a debate for the ages, one not lost on Truman that was pretty unnerved when he visited Germany after the war, but really the alternative was starving Japan even further, bombing what was left only with conventional explosives and repeating the horrible experience of Okinawa on a grander scale.
As for any possible Obama statement, I expect at best something carefully crafted to appear sensible to human pain and the lessons of history without appearing like an apology. The nuance of apologizing to survivors and not to the official institutions is way too minute.
