The number of users by instance in #mastodon is highly unequal. Some servers (mastodon.social) have a significant fraction of the number of users. If the ubiquitous "rich-get-richer" (RGR) phenomenon kicks in, we might end up with a couple of instances having all of the users. But did it kick in? Here is the relationship between instance's size and growth. There is a little bit of RGR, but some of the rapidly-growing instances are small. Decentralization also in how the network grows.
@estebanmoro
I think one advantage of #mastodon over other types of #fediverse instances such as matrix or nextcloud is that mastodon server have a kind of profile (agenda, common interest of users) that gives people a criterion to choose a certain instance other than user count. I suppose this will help keep some kind of balance.
