This seems like the opposite of free speech being dead. A website shut down and you can just... go... make or use another one, anytime you like, without having to worry about it even being illegal.
I also see this as a market opportunity for a startup to adapt / improve on tumblr and fill the void. An unexpected, and permanent content restriction on a major platform is a disruptive event.
Yesterday's BitChute discussion [0] brought up the unfortunate fact that many ostensibly free-speech zone sites such as Voat and Gab just end up being havens for far right bigots and conspiracy theorists. Made me wonder if that toxic stew could be balanced if far left activists brigaded those platforms. With this story, it'd be even more amusing if amateur erotica creators and kink community people migrated from Tumblr to those places as well.
Interesting thought experiment but based on my understanding of online community behavior I highly doubt erotica creators would go to a place already entrenched with Qanon believers.
I do think they would jump to “the new tumblr” not owned by Verizon that has its own cool culture. Both consumers and creators like building stuff up.