What advantages and disadvantages does upgrading Python to a newer version not available in the Distro bring. For example, upgrading from 2.6/2.7 to 3.1/3.2. Since there are several questions relating to problems because of this, or a necessary to do this I thought it would just help in concentrating the benefits and problems associated with upgrading Python to a new/older release.
The main reason you'd want to install Python 3.x is to run Python 3 programs. With that said, you would still need Python 2.x installed if you wanted to run programs designed for that language since there are incompatibilities between the two.
As far as picking a single default Python interpreter for the base install (with the other needing to be installed afterwards if needed), the main reason you might want to pick 3.x is that this is where the language evolution takes place.
As has been announced, there won't be a Python 2.8 so any useful language extensions added to the 3.x branch of the language are not going to be back-ported to the old language.
Programs depending on Python 2.x are not going to go away any time soon, but the code in the default install is a much more manageable quantity. So switching over should be possible in a much shorter time frame.