I don't think a stable ABI has enough advantages to be worth it. C++, IMHO, is a great examples of the downsides of a stable-enough ABI, where stability was never guaranteed, but is now so entrenched that it'll likely never be broken again (limiting the language & the usability in a bunch of ways).

It might make sense to have a subset Swift-style stable ABI, but that's a huge engineering effort, has lots of overhead and is also likely not worth it IMHO.