I'm sure this is a subject that's on most python developers' minds considering that Python 3 is coming out soon. Some questions to get us going in the right direction:
Will you have a python 2 and python 3 version to be maintained concurrently or will you simply have a python 3 version once it's finished?
Speaking as a library author:
I'm waiting for the final version to be released. My belief, like that of most of the Python community, is that 2.x will continue to be the dominant version for a period of weeks or months. That's plenty of time to release a nice, polished 3.x release.
I'll be maintaining separate 2.x and 3.x branches. 2.x will be backwards compatible to 2.4, so I can't use a lot of the fancy syntax or new features in 2.6 / 3.0. In contrast, the 3.x branch will use every one of those features that results in a nicer experience for the user. The test suite will be modified so that 2to3 will work upon it, and I'll maintain the same tests for both branches.