Well it certainly could be argued, but not one pro is anywhere near his genetic limit (they are all WAY over it). All the genetic limit implies is that is how far you can go NATURALLY. Todays pros are on all year round, so they are probably the worst examples to use...
But if these guys were forced to come off for 2 years (with no BB'ing drugs whatsoever) they would probably revert back to that "ceiling" again, and be nowehere near where they are at now...