Fork wars seem likely for any open and distributed network project. Although the value of a network is directly proportional to the number of people on it, so one fork tends to dominate and subsume resources from the others until they become a husk hobbling along. This chaos isn't necessarily bad, it's just the nature of a network that has no centralized, controlling authority to settle disputes. It's one of the tradeoffs you take when deciding to avoid centralization.
It's still early enough that fork wars in Mastadon seem likely, and would take years to settle. When the first bitcoin fork happened, bitcoin cash, happened in 2017, it peaked at a value of about 25% of the main chain. Today it's value is about 0.5% of the main chain and it is effectively irrelevant.
There are multiple forks of Mastodon already being run on live servers, often ad-hoc forks with minor tweaks. If you define fork narrowly enough, even changing the character limit might count, and quite a few servers do that.
Most forks do not break interoperability, which is very different from Bitcoin forks.
Beyond that, Mastodon interoperates with other software that speaks ActivityPub like Pixelfed and Friendica.
But what would the forkers gain? Bitcoin doesn’t seem interesting as a precedent because there’s no financial gain in forking Mastodon. The currency of the fediverse is user content. If you can’t or don’t interoperate, you lose all of the content.
It's still early enough that fork wars in Mastadon seem likely, and would take years to settle. When the first bitcoin fork happened, bitcoin cash, happened in 2017, it peaked at a value of about 25% of the main chain. Today it's value is about 0.5% of the main chain and it is effectively irrelevant.