Thank you for writing us about this, and I'm sorry for the delay in getting back to you. We are hoping to publish a new edition of Python in a Nutshell, but do not have concrete plans or a date for it yet.
We do have some other Python books that have been updated for Python 3.0, like Learning Python, 4th Edition and Programming Python, 4th Edition. Both of those books, and some other Python titles, are on sale today: http://shop.oreilly.com/category/deals/python-think-complexity.do
Thanks for letting us know you'd be interested in an updated edition.