If the effect is so widespread, surely it'd be financially irresponsible for any company in their right mind to hire men because women would negotiate less in the middle and long terms.
I think most managers would see that as an unreliable prediction to make, and not very valuable when making hiring decisions. When hiring someone, you are solving an immediate problem, and not often thinking of the future raises the person is going to negotiate or not negotiate.
What you are saying might be true if most hiring was done by CEOs and not department managers.
What you are saying might be true if most hiring was done by CEOs and not department managers.