That's because a Linux kernel maintainer was a jerk to the project's lead, causing him to quit. It was a Rust argument, as I recall. Also, their genius graphics dev got hired into a large company, though I don't recall who.

I don't have a lot of insight into who is working on what. I only know of these two people because they were noteworthy enough for articles or HN links to make me aware. That said, a lack of developers isn't the same thing as constraints from Apple. If you get people who are motivated to continue building Asahi, it absolutely could continue to expand to newer chips.