For obvious reasons, you're not going to see mask mandates for flu season. It's simply not contagious enough. I think there will be more social pressure to wear masks when you're not feeling well and an increased acceptance of staying home when sick though.

Sure, but do you really think people who won't wear a mask when it's literally against the law not to will wear one voluntarily?

I think it'll be more a matter of "I don't want to get sick and I'm your manager, so {put on a mask,stay at home until you're no longer sick} or stay at home forever".

This is indeed how it works for the healthcare industry; when I was doing hospital IT, my choices during flu season were either 1) vaccinate, 2) wear a mask, or 3) find a new line of work. I picked the first one.