I kinda agree with detroitjohn - Jimmy has a VERY long leash here in Ann Arbor. We all know that he is a fantastic coach but he's also completely nuts and I think he can rub folks the wrong way - college is perfect for him because kids know they have to put up with him for 4 years only. Furthermore, he is adorned in AA and he is in control - that situation does not really exist in pro football unless you are Bill Belichik. Even John Harbaugh will start to be questioned this year if his team goes 8-8...that's just the nature of the NFL - you are so dependant on an owner and GM being able to fork out money and have the right mentality versus in college where you have a greater span of influence if you are a coach like Harbaugh.
I also agree that cirumstances change, things change - family situations come up so you never really know but I think he is at peace and I think he will likely be around for another 5+ years at least. Biggest risk with him is his staff - he hires really well and as he succeeds there will be turnover over there at a higher rate then most schools since most of his guys have NFL pedigree but I am sure he can manage that well.