While the topic raised in the versioning scheme thread mentions a general API version possibly separated from the program version, bug #448285 "lxml version bundled with Inkscape is old" https://bugs.edge.launchpad.net/inkscape/+bug/448285 brings up an issue that could be discussed and solved for 0.47 (especially as 0.47pre4 has just been branched).
Could there be a central document on Inkscape.org available for all future extension developers (and package maintainers) that defines the python version and necessary python modules for the current release and lists the minimal versions every Inkscape installation needs to provide for the extension-system out-of-the-box? Or could this be handled entirely by the configure and packaging scripts, which then create an updated 'README.python' document included in the 'share/extensions'?
~suv