One of the tumblr replacements some people are working on is called MojoFire. It’s still not live yet, but they seem serious about making something of it.
The reason I mention it now, is that they’re offering tumblr users a chance to claim their same username ahead of anyone else. You can do so here if that sounds interesting.
Naturally I can’t vouch for any of this, they’ve been rather light on the specific details to be honest, but assuming it works out, it will presumably a) be somewhat similar to tumblr, and b) allow adult content. Don’t really know anything beyond that.
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