As Letterman so adroitly put it, you can't suspend the Presidency if there is a crisis. For those independents who didn't already know McCain makes hasty and rash decisions, they ought to have a pretty clear picture by now, and that appears to be evident in the polls. Survey USA polled on it, and most Americans think the debate should go on.
Well, if McCain is too busy being in DC to help with a bailout when he is not even on the senate committee tasked with it to debate tomorrow, I say let him - with one caveat.

Obama should have this opportunity to answer the moderator's questions himself, with full airtime from the media. If McCain isn't there to counter, too bad.