Whether he does the debate or not is irrelevant. If he shows up, he wins. If he doesn't show up, he still wins. He can show up and say " I didn't want to let the votes in Iowa down". If he doesn't show up he'll say "I believe that the wounded warriors are far more important than yet another silly debate with too many candidates on the stage." Meanwhile everyone is talking about him.
The media are his chew toys. He chews 'em up and spit's 'em out when he's done playing with them. He is running a brilliant campaign.