Yeah, they started rolling it out more thoroughly not long ago. I've got a little "Post+!!!" icon dealy in the drop-down menu for personal account related stuff (followers, drafts, settings, etc).

Honestly, I'd be satisfied (to the extent possible) if Tumblr made absolutely certain to clarify that profiting off of fandom content through Post+ was not allowed, or at least horribly fraught, but I already covered how I'm not expecting them to get rid of it entirely.