Seems unlikely. It's in opposition to Mozilla's clearly stated stance toward privacy.

In addition, their reasons for deprecating their old extension API was purely technical. Even then, they were extremely conservative in their deprecation timetable, waiting long past when the old API was massively harming performance. But once they made the decision to replace it, it made sense that they would choose an existing API as a base, not make a separate incompatible API.

But do note that, while Firefox and Chrome share the same base extension API, Firefox has APIs Chrome doesn't. It's reasonable to believe that this new deprecation will just become another thing that Firefox has and Chrome doesn't.

Yes, that sounds exactly right. But I would add that there is a technical reason for the more limited blocklist setup, in that it's much more reasonable to do a simple list check asynchronously than to run JS code.

But to me, that just suggests that firefox might want to consider an additional async API. I can think of many options that are more powerful than what Chrome is moving to. eg use the exact logic uBO needs. Or register a WASM function with no access to anything that would problematic to run async.