I don't see the problem: only 3 members of that namespace are currently claimed (4 out of the 36-member namespace: 7z), so we have room for 23 (or 32) more comp

I don't see the problem: only 3 members of that namespace are currently claimed (4 out of the 36-member namespace: 7z), so we have room for 23 (or 32) more compression standards before running out. We've been using gzip for, what, 20 years now? Only recently have we gotten xz. At this rate, we won't run out of compression standards using this scheme for roughly 153 years. And after that, we could always start using capital Zs, like the old "compress" standard that used the .Z extension. Or we could go to a 3-letter extension ending in z, such as ".fbz", which gives you 676 more options, and 4507 years. Considering that general-purpose data compression really hasn't moved that much since the DEFLATE algorithm took over, and only recently had any real change with the advent of LZMA (used in p7zip and xz), and perhaps this new zstd (too soon to tell), my time estimates here are probably too short.