That is, I think, a valid point.
There are some murmurs here and there that McCain has been skipping a lot of practice sessions in the run-up to the debate, and just simply isn't prepared. Given his past record of academic achievement, this is a bit more believable.
That would explain his request to delay, and the fact that he has canceled almost everything.
He just might need the time to get ready. Obama has been disciplined and prepping for quite some time, much like you would expect from a guy who graduated Harvard Law school.
This would explain why:
McCain has felt the need to cancel everything and push back the debates, even though he is not central to what is going on, and Obama wants the debates to go on.