Google has just released the App Engine SDK 1.7.3 which these col features: fully support Django 1.4 on Python 2.7.
It's good to hear that now the latest release version 1.4.x of Django can run on Python 2.7, and not lagging much on the support for the latest Python 2.x family. This is what I've been waiting for!
The full release notes is at here.
I am going to try get my hands on it!