If not in the actual epsiode then certainly on TV in some fashion that same evening. Mr. Davison has stated (including when he visited WhoNA last month) that he would be involved in celebrating the 50th Anniversary even if he had to produce a special himself. But he also stated that he's under strict orders not to reveal anything about the special. And I wouldn't want him to.
75minutes / 11 Doctors = incoherent story. All the Classics won't have full parts, but the hints are great that there will be Classic Doctor participation in some fashion. I'm hoping I'll be pleasantly surprised at whatever this special turns out to be.