I don't know what's the decision (if there is one) about situations like
these. If the bugs in lang-mode are fixed by lang-ts-mode, will these
bug reports be treated as: wontfix? fixed? open in case someone wants to
spend time in lang-mode?
AFAIK we don't consider the `foo-ts-mode` to obsolete the other modes.
Maybe we will, but we don't yet. IMO I think we'd first need to have
a good long-term strategy about what we'll do when tree-sitter becomes
unmaintained/obsolete. IOW I think we need to develop our own layer of
abstraction above tree-sitter so that we can accommodate other
parser backends.
FWIW, it's not clear at all what such a layer would look like, so we're
pretty far from it. I'd welcome people start thinking about it, maybe
by looking at existing alternatives like our own `wisi` (in GNU ELPA),
SMIE, maybe LSP (assuming there are servers out there which can provide
that kind of functionality), etc...