Xenofarm is relatively easy to whack into working atop a subversion repository (probably goes for a git repository as well); that is just a swift untangling it from fraternizing with the cvs browser.
For convenience, as that was a painstakingly slow operation in cvs, it asks http://pike.ida.liu.se/development/cvs/latest-Pike-7.<X>-commit for an UTC timestamp once in a while when it feels ready to generate a new build package, checks out the source tree matching corresponding timestamp (unless it felt it would be better to sit quietly waiting out quick fixes) with cvs -D, and that's all the integration there is to it.
(The files doing this are in pelix:~xenofarm/xenofarm_cvs, and to be quite precise, projects/pike/server*.pike, one matching each project.)
Getting the much less essential (though admittedly comfy) cvs browser up to par with the new repository reality won't happen as instantly, or will at least require some serious hackery to cater the different basic assumptions of whatever non-CVS/RCS version control system gets adopted instead as new world order.
With git, I presume the idea is that the command-line client replaces the comfy web UI, and those with a working X server setup get gitk too for snazzy visuals (I don't, at the moment, so I've only prodded at the less sexy command-line tools) on top.
With svn, it probably hurts a bit more, unless someone sets up Trac or similar, which has a fairly decent (if somewhat short of good) web UI of the same approximate type as the current breed of CVS browser. This stuff in practice needs us to change VCS backend before anyone will do it, as it's really boring work nobody got to doing while stuff worked.
All in all, Xenofarm can be up and running on whatever-else in no time (if proponent-of-whatever-else pokes at it for half an hour), and web visualization of commits (and checkin graph eye-candy on the pike site root page) will have a period of down time until someone puts in some love to that end.