IANAL, but I believe that what will happen is that those patent sales will be encumbered by the existing agreement, and accordingly less valuable.
If the new patent owner tries to sue people who relied on Microsoft's prior promises not to sue, it might be possible to accuse them (Microsoft) of promissory estoppel and force them to cover any damages. It's probably not in Microsoft's interest to play games like this.
If the new patent owner tries to sue people who relied on Microsoft's prior promises not to sue, it might be possible to accuse them (Microsoft) of promissory estoppel and force them to cover any damages. It's probably not in Microsoft's interest to play games like this.