I think the best we can hope for in the long-term is an email-like adoption.
Individuals self-hosting major servers on donation money is not sustainable. This sucks for the people for whom this is “what Lemmy is”, but it’s the truth. There will come a time when Lemmy-at-large gets so big that Lemmy.world has to close (or de-federate), as users and content will outgrow voluntary revenue.
What we can hope for is that Lemmy is not taken over by one huge corporate instance, but instead 3-4 competing, inter-federated corporate instances. A Meta instance, a Google instance, and a Bytedance instance, for example. In addition to these, smaller (non-social-media) companies and institutions (game companies, universities, political organizations, etc.) would run their own Lemmy instances for the benefit of their members and users.