[sending this independently to python-dev and core-workflow]
I have promised Ned that we will not migrate before 3.6.0 is released and not for a week following in case an emergency 3.6.1 is necessary. I also promised Larry we wouldn't migrate the week before 3.5.3 is released. That means the windows for migrating are 2016-12-30 to 2017-01-09, and then any time after 2016-01-16 (this of course assumes all release schedules don't slip).
I'm now on vacation until January 3 so I will have time to work on the migration some more. I will port hg.python.org/lookup to work with git, hg, and svn probably this week or next. That leaves the only true blockers as http://psf.upfronthosting.co.za/roundup/meta/issue589 and http://psf.upfronthosting.co.za/roundup/meta/issue590 (webhook for PR to issue and notifying an issue when a commit has occurred, respectively; we already have a GitHub PR field on b.p.o for manual entry). Once those changes to bugs.python.org land and have been tested live against the GitHub mirror, we can do the migration (which will most likely take a day or two). All other issues either require the repo to have already been migrated and working or can wait post-migration ( https://www.python.org/dev/peps/pep-0512/#cpython-repo).
So if the above wasn't clear, if you want to help then please help with the b.p.o issues as those are the remaining blockers I can't deal with on my own. And I actually have GitHub-themed gifts I bought myself sitting under my Xmas tree that I won't open until we migrate, so let's not take too long. ;)