This time, Threads is a fully fledged app. Getting users to adopt a new app might take as much time as getting Messenger installed. Still, Instagram has a robust social graph to lead users towards downloading it. In fact, they seem to have already onboarded users when they implemented part of Threads with the status update feature in the Instagram messages view.
Twitter will probably remain used by relatively "anti-social" people. In the States, that may be by politicized users, fueled by Elon's freedom fighting. Here in Japan, Twitter is very popular because of the sense of anonymity, coupled with the use of Kanji characters that achieves concision within 140 characters. Instagram might be too social for us (esp. male older than 25).
It will probably pain me to see the diaspora of users among many microblogging services. The transition to a new microblogging hub may be painful for both Twitter Inc (ie. X Corp) and Twitter users.
It's funny to see that Threads is the re-implementation of Facebook status updates before news articles swamped the Newsfeed. Meta's microblogging came back full circle.