Not more than it is now. Everything is already public so if they need it, they’ve already been collecting it. This doesn’t really change anything.
And it’s how federation is supposed to work. Either you want to send your content to other instances or you don’t. But federation is the wrong tool if you want to stay alone. You can defederate and block them if you don’t like their terms.
Couldn’t instances or accounts just license their content? Like would it be legally binding if I write in my profile that all the content I wrote here is licensed under a specific CC license?
It aleady has been. Anything, anything publicly posted and available will be harvested by, at a minimum, Google spiders. The only privacy benefits of any site can only be promises that they won’t share the information that you don’t publicly list.
And even then,.all it takes is the feds raiding a dipshit Kolektiva admin to get that information illegally anyways.
Do not organize serious actions over social media. At most, hold sensitive discussions over private, E2E encrypted chats like Matrix.