10% of Python devs is a very large number of people and it'll only grow larger. Python 3.4 is very pleasant to work with and library support is pretty good (I'm working on a py3 code base daily.)
At monthly PyDataLondon meetings I remind the audience to switch to Py3 (a few do each month) as Py2's sunset date is less than 5 years away now.
Back in April 2013 (the last time I saw python.org download stats - where did they go?!) I wrote a blog post noting that fresh downloads of Windows Python 3.3 were greater than downloads of Windows Python 2.7, for 3 months running. Windows is useful as Python isn't bundled (unlike e.g. Linux and Mac). I presume this trend has continued but have no firm evidence either way: http://ianozsvald.com/2013/04/15/more-python-3-3-downloads-t...
What do the PyPI stats say?