hmm...
Well, in my opinion, an All-Stars edition is definitely a sign of maturity, because a show has to have been around for a while to generate enough 'stars' to pull a cast from.
But All-Stars editions are notoriously over-hyped and therefore usually a disappointment. So I don't think the series would end on this "high-point" you speak of
I think of All-Stars editions more as turning-points and place-markers. Usually it means the staff has run out of casting twists and resorts to an A/S edition. When that flops, something happens (maybe they fire and then hire new production staff??) and the show gets revitalized for a time with new casting twists.
Or at least that is what seems to have happened with Survivor. We'll see about Big Brother next summer.
I would hate to see the end of The Amazing Race. But I would like to see a shake-up or two. They had a couple of new twists this season, but I don't think either of them were so drastic as to change the basic game play.
My favorite thing about the game play this season was the elimination of racers begging locals for money. I always thought that this was in extremely poor taste and morally suspect.