I do still regularly use Tumblr, and I can tell you: Tumblr users have a violently negative reaction to the idea of the site becoming more like Twitter. Trying

I do still regularly use Tumblr, and I can tell you: Tumblr users have a violently negative reaction to the idea of the site becoming more like Twitter. Trying to force through that change would destroy what little (commercial) value Tumblr has left. Just let it be its own thing, and if you want to make another Twitter, go build it somewhere else.