I don't think skipping this debate is the right decision.
During the last Nigerian Presidential election, a friend of mine who'd witnessed the event said that the opposition candidate found the debate unfair somehow and boycotted the debate. The result was that Goodluck Jonathan had the stage entirely to himself and just spoke the entire time. It was basically an hour of unrefuted, free advertising, handed to him by his opponent. By skipping the debate, it may allow the candidate to score a few feel-good points against Donald Trump, but that isn't the point now. The point is to build up as much momentum as possible leading up to the Iowa caucus, and that means fighting tooth and nail for every bit of oxygen that you can get your lungs over.
The Nigerian debate wasn't moderated by Donald Trump, and I have a feeling the moderator didn't use the forum to flaunt his hard-edged style and ask self-serving questions. Any event hosted by Trump is about Trump. Period, end of story. The man is a mediocre businessman, but he excels at self-promotion.
It's very smart especially in light of Paul and Huntsman bailing on it. Now it'll be 1-3 conservatives attacking Newt viciously 1 week before Iowa. I assume Bachmann will attend. Perry is a big question mark. He's desperate for any chance to redeem himself but also one more bad debate and he's finished for real. I wonder if he skipped it, if they'd still have it.
I doubt Perry will show: he'd be well advised to take pretty much any excuse to skip a debate, seeing as his debate performances have taken him from front-runner to national joke.