Trust me, if they thought they could get away with doing it, they'd have done it a while ago.
They know they're losing the public really badly right now. There are already cracks appearing in the armor. They're asking for the unvaxxed nurses and doctors back already. They can't sustain this with this level of resistance, which is growing, and they know it.
They can amplify everything with their bullhorns, but the rate of people going back for boosters is abysmal, less than a third of the people who got their shots have gotten boosted.
They'll threaten it, just to get you to take your shots, "because I simply HAVE to travel for work/family/etc". But, I'm calling their bluff on this one. I don't think they can weasel that one through.
I hope I'm not wrong on this, but I'm actually fairly optimistic on this one.
Maybe.
But remember, the pharma industry makes what the airline industry makes in a year, in a matter of months. Pharma can outpace other industry caps and use that excess to buy influence for pennies.