Well, apparently this year was just too much for Gibbs, and in all honesty, this decision is hardly surprising or shocking.
It doesn't mention it in this article, but Chris over at arrowhead pride noted the following about current Redskins Defensive coordinator, and former Broncos coordinator, Gregg Williams:
His 2006 contract extension stipulates that he will receive a $1 million bonus/compensation if he does not succeed Joe Gibbs as Redskins' Head Coach. He must still be with the team at the time of Gibbs's retirement.
Not a lot of money, but mucho interesting if you ask me. I can just see him turning to ask someone what he should do and...no ones there!
Just keep doing what you've been doing, Gregg...