I don't think anyone's taken over development. It was sad, but I've moved back to using emacs after using jedit for ~4 years. Here are some pro/cons that I re-discovered, for out-of-the-box experience (I realize you can "do anything" if you code enough elisp, but that's not what I'm talking about).
jedit pros: 1. GUI is nicer/exists - fonts, dialogs, etc. 2. (Simple) configuration is nicer. 3. Has more editing features readily available (I hesitated to include this, given that I'm comparing against emacs, but I did find that I discovered useful features more easily by browsing the jedit config/docs than with emacs through apropos/texinfo)
emacs pros: 1. Editing modes are more polished - python, and especially auctex. 2. Remote/console use. 3. Less memory intensive.
A con for both is still occasional unresponsiveness. The reason that I left emacs to begin with was that at the time I still read my mail through emacs, and the fact that emacs was single-threaded meant that whenever I did something "intensive", e.g. open a large mail folder, my entire emacs would stall. I felt like I needed to move away from the emacs- is-my-OS workflow. Now that I've come back to emacs and use it soley as my editor, it's not nearly as bad (and computers have gotten faster in the meantime too :-), but I still find the occasional inability to edit another buffer while emacs does its thing annoying. On the other hand, jedit, being a java app, seems to want a ridiculous amount of memory, and hence I encountered random hiccups from (I'm guessing) gc.
Anyways, I think the main advantages and disadvantages of emacs stems from its age - it has a lot of nifty polished packages, but its base architecture AFAICT isn't really conducive to threading (or whatever other technology you want to use to enable snappy multi-task/buffer work environments).