Predictable is in the eye of the beholder, but the aerobatic PILOT who cannot predict the next maneuver is already dead, he just doesn't know it.
I flew an aerobatic routine in the Paris Air Show once, and in the 20 or so times I flew it (practice at the show, qualification trials with show officials, and in front of the crowd) I was never more than 1 second off in a 3 minute and 11 second routine.
To support Rich Lee (who has done far more than his share of this silliness) if the pilot is not flying a rigidly practiced routine, he is in vast trouble. The Crowd should find him unpredictable, but his CP had better not.
Regarding the qualification and certification, the FAA requires a "Certificate of Aerobatic Competency" that is issued by one of their examiners, not an easy certificate to earn, since the examoner puts his or her reputation in your pocket when you fly. I carried around one of these for several years while flying various models in airshows. I know the US Red Bull pilot, he is a real pro, and nothing he does is without cool professional, predictable deliberation.
The FAA also requires specific approval for each demonstration before a crowd.