I don't think he's necessarily at more risk of injury than the others. But there's always a risk of injury, and if it happened to a 50 year-old Holyfield it would be worse publicity for the fight game than if it happened to a 30 year-old contender unknown to the mainstream. Sure, he hasn't got much chance against the Klitschkos, but nobody seems to have at the moment.
I feel like a Holyfield/Arreola fight would actually sell pretty well by American Heavyweight standards. With all the hype Arreola has gotten from HBO and Holyfields name I wouldnt doubt it if they could do an HBO undercard and draw some viewers