This has happened time and time again with most SaaS, and will continue to do so, unless some new model arrives where each user can run their own version.
I had two slack workspaces for completely different projects/companies. I set the other one up early this year and we were slowly migrating to it after another SaaS went bust.
I was going to start paying for that workspace too, because I needed the extra features. Luckily they showed their true colors first and I got a chance to migrate away early. I don't want to deal with their whims long-term.
Honk honk.