then there's appengine, just now got up to 2.7. it will probably be another few years before it's on 3.x. doesn't fedora still ship with 2.4? ideally we would all like new toys, but reality sucks most of the time.
You're confusing Fedora and Red Hat. Fedora is generally very cutting edge and has been shipping with 2.7 for quite a while now, Red Hat is far more conservative and was, at least up until the latest release, shipping with 2.4
Fedora 16 (the latest) ships with Python 2.7. Python3 is available in the yum repositories.
Distros aren't holding Python3 adoption back, it's apps and libraries.
As far as I can see, they're shipping both 2.7.2 and 3.2.2: http://pkgs.fedoraproject.org/gitweb/?p=python.git