Funnily, though, I just thought 'yeah there's that library I use, they never ported that', for one of my codebases. Just looked it up and they now have ported it. So I guess it's time for me to do the same. I wonder what proportion of (actually used) libs are Py 2 only still.
For those who don't know: http://python3wos.appspot.com/
The entire scipy stack, ntlk, tensorflow has partial 3.0 support and plans to support both, caffe, theano, etc.
There are few to no libraries that don't support, or don't plan to soon support both.
(Edit: Not that I care what they use internally... but sometimes they release a really cool open source library and it is Py2 only... arr! But at least they are sharing, so I can't really be too upset :)
There's really no good reason not to support Python 3, and projects which refuse will at some point be forked.
I suspect this is just an issue of they didn't want to block the release on not having Python 3 support ready at launch.