Eventually the old man is going to get out of his wheelchair and step up to the podium. It would be considered unprecedented, and in fact cowardly, if he totally ducked debating Obama. Especially considering that he issued those challenges to take Obama on a tour of town hall meetings.
His goal, IMO, is to delay the first debate for two primary reasons: He doesn't want to debate Obama in the medium of this climate: a complete meltdown of conservative economic ideology. He does NOT want to take that podium, and have american people reminded while its fresh in their minds, that he was a tool who went along for 26 years with Reaganomics, S&L bailouts, union busting, and deregulation.
His secondary goal is to either delay the Palin debate, to buy her more prep time (God, does she need more prep), or preferably to cancel the VP debate althogether.