Agreed. When Instagram added stories, my entire Snapchat friendlist disappeared within a month and they were all posting to Instagram instead. I think the same will happen here. But it will be lopsided toward people who are already more popular on Instagram than they are on Twitter, which is a lot of social/non-professional audiences. I expect that Twitter accounts with large followings will continue posting there, and Twitter will continue to dominate the professional niches (coding twitter, medical twitter etc.) while the more general shitposting and possibly even politics will move to Threads.

I say this as someone who is no big fan of Meta.