I’m not suggesting that they should replace Lemmy as the backbone software of the threadiverse.

Interesting, because that's what I could see happening once they catch up. Unfortunately that's not for now.

I expect Sublinks to eventually overtake Lemmy since it’s being designed as a drop-in replacement, in a language better suited to web development than Rust.

Sublinks was announced in January 2024. We're in September, and the 0.1 version still isn't going to be released any time soon: https://github.com/orgs/sublinks/projects/1/views/6

I was hopeful for Sublinks as well at the beginning, but it seems like it's not going to be the one replacement a lot of people were waiting for.

At this point in time, I think Piefed has the highest chances at becoming a 1:1 Lemmy alternative. Development has been fast. Maybe in 6 months or a year it can really reach feature parity.