TL;DR it will grow. Twitter/FB will remain the largest players but become increasingly censored and uninteresting; clusters of Mastodon instances which don’t federate with each other, as well as other services, will absorb the resulting exodus. 2023 is a future where social is fragmented.
If you look at the adoption pattern and growth rate of Mastodon, it has around 1.5M users, the majority of which have arrived via three big waves.
The first wave was people with left wing identities who were tired of being harassed on mainstream platforms like Twitter.
The second wave was Japanese lolicon enthusiasts (without diving too deep down this rabbit hole, lolicon is a popular but weird and nerdy thing to be into in Japan).
The third wave was sex workers in response to SESTA/FOSTA eliminating platforms they used in the past.
All these waves set up their own instances, and they don’t communicate much with the other waves.
If you look at what these waves all have in common (aside from using the software), there’s just one thing. They were all posting stuff that didn’t fit in on a mainstream platform. In the first case it was due to harassment, in the second it was embarrassment, in the third it was legality.
The users are already bifurcating the network, admins routinely share blocklists of sites that they don’t want included in their version of the fediverse. Being able to block instances and people you don’t like is one of Mastodon’s killer features.
I don’t think it will become the next outrage machine, people will just block and bifurcate. I do think users will keep setting up Mastodon instances in waves similar to the first three. I’d be surprised if Mastodon ever powered a better version of the commons we currently have on FB, Twitter etc.  The feature Mastodon added to federation (and that made it more popular than similar software) is the ability to not federate with people who are different from you.
 The “fediverse” at large has some potential to do this if it receives mass adoption. Think of a scenario like WordPress integrating federation features into the Core. This would bring federation to the mainstream.