I guess I would like to get to point where basically current ghc9 would correspond to Stackage LTS and ghc10 to Nightly.
Well I guess forward-looking I really mean: ghc10 would be stable (ie the same Stackage LTS major version could use GHC 10.1, 10.2, 10.3, 10.4,… minor versions). Whereas GHC nightly might live in Stackage “experimental” (nightly) say.
This would require a complete change of versioning and releases of course. New features could be gradually backported as needed/desired to stable releases if they don’t break stable GHC.
In the ideal stable world, ghc10 would then be the last final stable major version of GHC (à la rust 1) ever.