(I have changed subject of your post to the new one, since I understand you'd like to talk about Xdebug, plus the new subject hopefully will attract more users.)
I'm not sure what exactly you have in mind when asking for Xdebug support. If you mean something as elaborate as is available in e.g.
PHPStorm or
Sublime, then the answer is no, and I can't imagine that this could be built with the current script engine. If you mean something simpler, what could that be?
I don't want to speak for Rickard, but I doubt RJ TE can ever get such deep native integration with Xdebug (or any other specialized tool), because RJ TE is, for better or worse, general purpose programmers' editor, not being aimed at Web design only.
On the other hand I would really, really love to see RJ TE open to solutions (e.g. plugins or color schemes) from other editors -- it would be great to be able to use ready-made, free components available on the Web. Alternatively, open architecture, that would enable users to write their own plugins, like it is the case with. e.g.
Notepad++.
I don't know what would be easier to design & code, and I'm not sure which solution would be generally better, but I suppose the former would be more realistic, i.e. using already written plugins. I understand that would require a massive re-write of RJ TE, though, while the latter could be introduced step by step.
(I wrote it in the past and I'll repeat it here: current scripting engine, i.e. FastScript, is a dead-end. It is not developed anymore and its documentation is severely lacking. Of course it is better than nothing, but all things considered in my humble opinion it is rather burden than asset.)
I would love to hear from Rickard on this matter, how he sees RJ TE in the long run, and I hope other users will chime in, too.