It's going to take ages for modules to get converted over... but most projects have been preparing for it for a while. However hopefully the migration scripts will get better over the 3.0 - 3.1 timeline.
For now I'm sticking with python 2.5 - since it's the best one considering it's far better module, and platform support.
You underestimate the power of the ... wait a sec. :)
Anyway, there's broad support and excitement in the community about this release. I think you'll see modules being updated more quickly than you suspect.
From the release page (http://www.python.org/download/releases/3.0/): This is a production release; we currently support these formats: ...
That said, I also plan to keep my core projects on 2.x for a few more months till django, ipython, debian repos etc. move to 3.x. But I do plan to play with 3.x some.
It's sort of a chicken-and-egg problem because without widespread use of 3.0 no one will feel pressure to upgrade their library. I'm hoping, out of the goodness of their own hearts, that everyone will upgrade their libraries (for no immediate benefit but the gratitude of 3.0 users!). Maybe a website badge should be created for this accomplishment!
Of course, that means making your code work with 2to3 to begin with, but that's a much lower barrier to adoption than outright porting and dual maintenance.