Well, I'd say switch just because all mainline development is now happening on the Python 3. I'm not too familiar with the development roadmap and which "features" might be useful for different audiences (e.g. the unicode overhaul and the asyncio stuff that landed in 3.4 are probably the biggest wins for the stuff I do) but I think just that reason alone is enough.

But I do think the biggest leap in adoption will be once Python 3 will be the default on most OSs, and we're definitely getting there. After we pass that, Python 2 will be the outlier, and Python 3 the norm.