I missed this thread earlier. I see the libproxy extension has one .py file in /usr/local/lib/python2.6/site-packages/. That directory is recognized by python-2.7, and should run from there fine as long as there are no .pyo or .pyc compiled modules in there. The C or C++ shared/static libs as well as the development stuff should work independent of python versions.
In this case, libproxy.tcz should work with python-2.7. Or possibly, the .py file could be split into a libproxy-python.tcz extension like Debian does it.
If an extension does not have a script that calls on a specific version of python, and has its .py files in a python path (site packages directories for either /usr/local/lib/python2.6 or /usr/local/lib/python2.7) it should work independent of which python is being used.
Perhaps on this python thing we can focus on looking for extensions that must be python version specific versus python modules that will work across either python version. If we want to keep the .pyc and .pyo files for performance, then we could separate the python modules out in extensions and then use the -python-2.7 suffix for 2.7.
Personally, I would prefer to not include the .pyc and .pyo files for the sake of portability and simplicity, allowing extensions to work with either python when possible.