You can download the sources from kde.org; those can be compiled against KDevelop 4.4 (which is the current stable version).
Changes over the first beta release include:
- Two crash bugs fixed
- Fix a bug in parse priority things (it did sometimes cause documents not to be reparsed after a dependency was changed, which led to imports not being handled correctly)
- Now full support for PyKDE4 and PyQt4!
Another note about the state of python 3 support: I'll probably merge the python 3 branch into master soon. All subsequent releases of master will support python 3 *only*. There will be a python 2 version of the plugin, which will be updated to work with new versions of KDevelop for quite a while (I'd guess at least two years from now), but I will not spend considerable time to backport features to that branch if they're not easily portable (I just don't have the time, sorry). I think my time is spent better on integrating the features new in python 3 and on polishing the new version instead of supporting two versions at once.
I also don't think it will be possible to have both the python 3 and the python 2 version installed at once, since that will require UI and logic for determining which version to use for what. I don't really want to write that, knowing that it will become more obsolete every day. If you really need it, you can still just install the two versions in two directories and start two instances of kdevelop (one for python 2 and one for python 3) with the two different install paths in $KDEDIRS.