I never have any idea what the codenames are, I know they are in a
release team announcement somewhere, but it would be great to just have
a list on release.debian.org, of future codenames, and maybe a couple
old ones too.

It's already on the wiki:

https://wiki.debian.org/DebianReleases#Production_Releases

Kind Regards,

Bas

true, but I don't find that when I'm looking for codenames. I know
release team does codenames, so my first stop to find them is
release.debian.org and then I lost and ask in #debian-devel or google.