The problem can be seen namely for KDE4 python packages - kde-base/pykde4 for example. The eselected python version has no effect, cmake always uses the latest one. The root cause is /usr/share/cmake/Modules/FindPythonInterp.cmake (part of dev-util/cmake) that looks namely for "python-2.6", then "python-2.5" and so on. It tries "python" interpreter at the last place, so the first found python version (the latest one) is always used instead of the eselected one.
Created attachment 177244 [details, diff] Patch to find eselected python interpreter first
Created attachment 177245 [details] Updated ebuild for dev-util/cmake-2.6.2
The ebuild just applies the attached patch, no more changes there.
Reasonable patchie. Added to the tree.
