The python-future does not support Python-3.2 because py32 does not support unicode literal. They said Adding support for Python 3.2 to future would likely impose a penalty with performance and/or maintainability,.. (see also python-future FAQ).
I think we need to decide whether drop Python-3.2 or not. If we decided to drop py32, we may not need to be dependent on six/future.
I've just finished porting Pygments to single-source, and I have two observations:
python-future's conversion tool is nice, but otherwise I prefer six: less magic. future even reimplements the "int" type which is definitely too much compatibility.
The u"" literal from Python 3.3+ is not definitely needed; modules with many literals can use from __future__ import unicode_literals while others can use a u() wrapper. For Pygments, I did not use unicode_literals since it pretty much changes all lexers. Therefore I require 3.3+ there.