If you aren't on the betas[1], that's a good place to start. I got an update today, haven't seen any new behavior yet, though.

1: https://slack.com/help/articles/226192087-Join-Slack%E2%80%9...

Asked support, rolled out over the "next couple of weeks." Typical fanfare, no way to opt in or out. No way of knowing when it'll all change, or the ability to give a heads up to your company.