Im 43 now. My bet is, that if I live to my expected lifespan of 75 years that the number of annointed will be about the same as it is now or even possibly higher.
Without the annointed there is no faithful and discreet slave. I know the Watchtower is already trying to move the mantel over to non-annointed ones, but I don't think this will be effective.
The whole concept of "The annointed", "The faith and discreet slave" class has a mystical appeal to it that the Watchtower cannot afford to lose.
Joel