You have a good point.
This would also prevent beginners from reading dev docs and accidentally trying to use features that are not yet available. I've seen this a lot.
Django fully supports Python 3 from version 1.5. If you can use it or not depends more on the other packages you might have installed like DB adapters, image processing, etc. https://caniusepython3.com is a good way to know, you just need to drop your requirements.txt and it will tell you!
Further, if you find a dependency that isn't supported, you should check the projects site to see if support is on the road map. You could also try contributing the python 3 upgrade to that package.
I recently began a new site based on django 1.7 (RC) and python 3.3, and only a single package I needed wasn't available. Someone had already opened a PR for py3 support though, so some gentle prodding got it merged within a week.
