A rewrite of many parts of Werkzeug is required to support Python 3. Might as well kill two birds with one stone :)
Edit: As a bonus link to make this post more interesting, the other day I caused the Python 3 version of requests to be packaged for Fedora 16 and 17: https://bugzilla.redhat.com/show_bug.cgi?id=807525
A rewrite of many parts of Werkzeug is required to support Python 3. Might as well kill two birds with one stone :)