What happens when a new villager moves in after you have 10?

Hmmm. You can only have 10 villagers at a time. You should have an empty lot right now with a sign in front of it that has a "sold" sign over it saying who is moving in.

Yeah I do. I met him at a Miles Ticket island.

Ah, I see. The only time a villager is randomly picked to move out is if you invite a villager that shows up at your campsite naturally.

When you invite a villager to your campsite via Amiibo card then you can choose who you want to move out and replace.