I have an email from the Stack Exchange community team, telling me that Winter Bash 2016 is ready, and will start on December 19, 2016. Because previous years have seen such a positive response, the default position is in - i.e. we will have hats.
If we don't want hats, we need to let the Stack Exchange team know by December 13, 2016.
If you want in, you don't need to do anything; that's the default this year, due to overwhelming positive response in previous years. If you want to opt out, have someone on your team reply to this e-mail to say so by Tuesday, 13 December 2016.
If anyone has objections to hats, please post them as an answer here so the community can make its decision.