> Twitter will continue to dominate the professional niches (coding twitter, medical twitter etc.)
I couldn't speak about "coding twitter" in general, but Apple developer Twitter in specific has almost entirely migrated to Mastodon (as well as a large contingent of the Apple news media). I see a lot of non-Apple devs there too.
I think this is a biased view held by people who migrated to Mastodon. In my experience on Twitter, the coding topics are as lively as ever, particularly around Web development. Personally, the introduction of the "For You" page has triggered me (very low following, previously inactive) to interact with accounts just because the algorithm does such a good job of surfacing relevant niche technical content for me.
I don't know about Apple Twitter myself, but Web Dev Twitter seems more active. Infosec Twitter was a notable niche that loudly proclaimed they were moving to Mastodon but in fact many of them are still quite active on Twitter.
