So basically you think using something like *.av1 extension for video/audio codec combo is not a good idea ? Better to name after container / technology ?
WebM itself is not a good name, because it implies web usage, while in reality those files are useful offline too.
How about using a new set of extensions to reflect offline use?
*.aov (Alliance Open Video; basically WebM but with AV1 or future codec)
*.aoa (Alliance Open Audio; basically Opus audio, but in webM container, like WebA)
*.aop (Alliance Open Picture; expected to be a future evolution of WebP)
Besides offline usage, another major consideration: future availability and deployment of AV1 hardware and software players are expected to be much wider than today's VP8/VP9, and it would be a bad practice to throw old VP8 / WebM videos at those new decoders.( many of whom will not play VP8)
-Alexey
--
-Alexey Eromenko "Technologov"