I actually feel this is gonna make it harder for people to find out about the change, having something suddenly disappear from your feed is less visible than having reminders when you click on a new post.

At the same time, cosidering the .org one is new, not a lot of servers/instances will have the community federated, so it will not appear even in the All feed for people, especially in the small ones.

For those reasons I would advice for a transition period, if possible, but I can see how it could be annoying to manage.