The "glass ceiling" or upper limit of 43-45 with BJCP scoring needs to be re-evaluated by the BJCP Board and consideration given towards issuing a position statement to all BJCP judges regarding the upper limit for scores in the BJCP guidelines.
I believe that a perfect score of 50 is difficult to achieve for the following reasons: 1) The score sheet is broken into six sections, so there are six places where you can lose points, rather than just one. 2) The judges have no way of knowing roughly how good the next beer in the flight will be, so they naturally hold back a bit to give the next beer in the flight a chance to be slightly better. 3) The need for consensus judging makes it pretty gutsy for one judge to max out his/her score and stick to it.
Practically, most homebrew (and most commercial beer) isn't "world class" and even "world class" beer might be conceivably be improved. The example you gave suggests that a "perfect 50" for homebrew is comparable to a "perfect 10" in figure skating or gymnastic. Consider, however, that a 10.0 is extremely unusual, even in Olympic-level competition. It's not going to happen in, say, collegiate or high school level competitions. Practically, most homebrewers are at the equivalent of high-school or college athletes in terms of skill.
I HAVE judged world-class beer (several beers made by a homebrew club members which went on to medal in the NHC 2nd round, a professionally made beer which went on to win 1st place in the Brewing News National IPA Challenge). I've also run training sessions where we judge commercial examples of great beers as if they were entries in competition. I'm not ashamed to say that I gave them well-deserved scores in the high 30s to low 40s. They were great beers, but there's always some way that they could be better.
Informally, I've described the upper scoring ranges for beer as follows:
34-36 Tasty, but trivial flaws. Equivalent to most craft-brews.
37-40 Superior. No obvious flaws. Better than most craft-brews.
41-45 Outstanding. World class. Angels sing when you drink this beer.
46-49 World Champion. National Best of Show winner. Angels sing and a beam of heavenly light shines down when you drink this beer.
50 Unique. When you open this beer, the heavenly choir sings, the skies are illuminated in holy light, the finger of God points down at the beer, and a booming celestial voice proclaims, "That one."