Yea they know that. Even in the face of that they are walking out. Must mean they’re seriously pissed off. I would be more worried if I were the employer depending on this office and I would be trying to make these people happy so all my projects wouldn’t go into the shit bin for several months while I tried to rebuild my team.
It is extremely important in these situations to distinguish between talk and action. So far you have a bunch of people talking about walking out, which is very different from doing it.