It could just be me, but I'm...really not convinced Pillowfort is gonna take off at all. It feels like people are pinning all their hopes on it because it's the most like Tumblr out of all available options right now, so I understand the hype, but I don't really trust them to know what they're doing.
I kind of think Tumblr will be limping along for at least another year or two before fandom abandons it entirely, porn ban or no.