I suspect that the only point at which I'll take down Noda Time is when Microsoft has embraced/reimplemented it and it's in the framework. I'd be absolutely fine with that.
Until then, I at least need to keep producing updates when there are new versions of time zone data.
Realistically, there haven't been many changes in the codebase since 2.0. I want to release a 3.0 which removes binary serialization and embraces Span<T> at some point (it may well only target netstandard2.0) but there aren't many extra features I really want to add. There's range-related stuff we might be able to do, and maybe there are some extra calendars we could add, but I'm pretty satisfied with the bulk of it.
(There's a lot of work that could improve the docs and web site, but that's somewhat separate.)