Pretty sure the plugin has a possibility of coming back and that there were just a few bugs that needed fixing with it, this would of course take time Cyp doesn't have to fix it, and I don't think that's happening any time soon, unless he can make the time, or find a new Dev, which is easier said than done. Also, this shouldn't really be in suggestions, because you haven't made a suggestion, this should probably be in "Help", as you're asking if it's coming back.
The plugin has some bugs so it's disabled for now. I'm unsure when it will be re-added. We put spleef in to replace mob arena for now. If you'd like to join spleef do /spleef join
