As far as I know, Gorhill has no interest in porting it to use a separate API, so effectively it will stop working even if in theory you could have a more limited fork.

I might be wrong on that though, please jump in if there are plans I don't know about.

It's surprising to me that Microsoft is planning to deprecate the old API, I thought their plan was to support both in parallel. Surprising and disappointing, I haven't seen any indication that the fundamental problems with the declarative API were ever addressed.