You can find videos of the Stig revealing himself to be Schumacher on youtube now...
Still... I doubt the Stig has been Schumacher all along. They probably have to pay more than what they are paying Jeremy Clarkson to get Schumacher to do the show and travel with the Top Gear production team regularly all these years. They probably just invited Schumacher to pull this stunt because this is the only person in the world that would not disappoint any fans of the show. My guess is that the true Stig is actually a number of professional drivers that take turn to play the role whoever has time when they shoot the show.
Still... I doubt the Stig has been Schumacher all along. They probably have to pay more than what they are paying Jeremy Clarkson to get Schumacher to do the show and travel with the Top Gear production team regularly all these years. They probably just invited Schumacher to pull this stunt because this is the only person in the world that would not disappoint any fans of the show. My guess is that the true Stig is actually a number of professional drivers that take turn to play the role whoever has time when they shoot the show.