For what it's worth, it was intended to be a slow transition (3-5 years) since it's a chicken/egg situation because of backwards compatibility.

The good news is that adoption should pick up very quickly after this fall. Python 3.3 will make it easier to port Python 2 projects and provide more incentives to upgrade. There's also nearly a critical percentage of major packages ported, and Django (which is still on Python 2, and is a deal breaker for many people) will have experimental support for versions up to 3.3.

I expect that by this time next year, the default for most new projects will be Python 3.