This has actually been done many years ago. http://django-nonrel.org . Don't know how it differs from this one, but it has many of the same features. Used it for a project 4 years ago.
Yea.. With Managed VMs You can run any VM on the App Engine stack which is f'ing cool. The most obvious use for this is Node IMO, since ppl have gone crazy for that shit. Soon the world will no longer need backend developers or dev ops.
It seems that Mr. Kurzweil has become very influential at Google. This is indeed the future that he predicts, and i can understand why google want's to be a part of that !
How is performance compared to using cloud sql ?