In reply to Robin.

Typically in deals like this, there's a stipulation in the sale agreement with a timeline. E.g., "Must be kept free for XX amount of months, years, etc."

I had a similar situation years ago when a company I was running was sold. Part of the terms of the sale was that current staff was to remain for a period of 1 year, (unless they violated company policies). It was a way to ensure a smooth ownership transition and prevent the new owner from just arbitrarily "cleaning house" upon acquiring.