Well, and I'm happily surprised to say this, Obama has apparently said he won't be apologizing.
I imagine he'll still be giving a speech about how horrible nukes and war in general is, which is fine, but he won't be apologizing to a people that were the Nazis of the east and tried to unleash plague on the North American continent. It's fairly clear Japan would have used nukes were they available.
This is why the whole "apology" thing needs to stop; it digs up old hostilities that don't even belong to us, but rather are the legacy of our ancestors. Otherwise, there's been strong relations for more than half a century now. Time to move on.