There is just one regeneration left that we haven't seen. Hurt - Ecclestone. I wouldn't be surprised if Ecclestone appears in this 50th anniversary special as one last surprise for the fans.
BTW. Now that we know, what is everyone's opinion of where the Hurt Doctor fits into the Doctors timeline? I was of the opinion that he'd be a pre-Hartnell Doctor, one before he "made the promise". Now that he's been shown as fitting between McGann and Ecclestone it means he made a promise, broke it, changed his mind and made it again.