Sounds like a weird reason to switch the language and framework used for your product. Blocking libraries block just the same in Node and in Twisted. Why not just stop using the Django ORM or more generally, stop writing code that blocks the main thread for long periods of time?

The problem of the main thread waiting on a response from the database is easily solved without rewriting all your code, which incidentally will have the same issues, since there's no new magic there.

If your software is a giant, ugly hairball because you wrote it in a hurry (I know I did this many times!) don't blame it on the language or framework. What I'm wondering is: Python/Twisted/Django rank equally or similarly on all the points from the list, except for Team Experience, which has to be much higher with the old stack than with a completely new technology and set of tools. This makes me think that there was a "play with shiny things" point after all.