I also wondered a little. I think the original creators and contributors moved on to other projects/technologies. I’m a part-time web-developer with enough Ruby-knowledge to use the Middleman and the likes, make some extended custom programming with it, but I have neither experience nor time to dig the internals of MM. I tried to analyze some quirks and bugs but never got the point of making a fix inside MM codebase.
But hey, MM is quite complete and very useful in its current state. I’ve made some research to answer my own question: should I migrate new projects to something new? I took another look at Jekyll, again, and decided to stay in Middleman. For my needs MM plus essential plugins and some my own code is good enough for the projects that I do. (Again, I’m not a full-time web-dev.)
Has anyone any alternatives to Middleman to choose from?