As we have discussed previously, Mike Zimmer is a very good coach. He has turned the Bengals defense into a tough, hard-hitting, smart squad that has been the basis for the Bengals turnaround this season. His contract is up after this season. After the family tragedy that Zimmer has suffered this year, he could very well want to move closer to family or take some time off altogether. But let's assume that Zimmer's top goal is to become a head coach, and if that is not possible, to take the most lucrative contract to remain a D coordinator.
As PFT points out, Zimmer's name has not been popping up for head coaching jobs. Perhaps this is because the media keeps focusing on more well known former coaches (Cowher, Shanahan, Gruden), but with Zimmer's stock sky high, he is sure to get offers from other teams to become their D Coordinators if head coaching jobs don't open.
If Zimmer has the desire and gets an offer to become a HC, there is not much the Bengals can do to to keep him in the Queen City. But it would be idiotic to let Zimmer sign with another team as their D coordinator.
The same PFT article links to a Bengals.com article where Zimmer told Hob that he has had negotiations with the Bengals in November, but "nothing came to fruition." And now Zimmer is getting interest from other teams to be D Coordinator.
The Bengals need to make sure that a higher offer doesn't cause Zimmer to leave town.
Unlike player salaries, coaching salaries are not covered by the revenue sharing or salary cap restrictions, which is why big spenders like the Cowboys and Redskins always have the highest paid coaching staff.
If Mike Brown and the Bengals want to make sure that this winning season is repeated, it's time to open up your wallet. Keep Zimmer.