If he doesn't take a head coaching gig in the next 12 months, then it's confirmed that he's one of those guys who is content to be a career DC in the vein of Bud Foster.
I agree. Bo should have realized that he doesn't like to deal with the administration, the media, and some critical fans. But these are the main jobs for a head coach. I worked with someone years ago that did some of the managerial work, but never tried to be a manager when a job opened up. When I asked why, the person replied, "You've been around here long enough to see what the company politics are like. I've been around here long enough to know I want no part of it." There are some people who need to figure this out before they make matters worse.
On the other side of things, some time ago I saw on this board that Craig Bohl made a better head coach than Defensive Coordinator. I still agree with that statement.
The best coordinators in football are obsessed with the X's and O's and carry as little ego as possible outside of taking pride in their own effort and attention to detail. A head coach has to deal with so much administrative and political b.s. that it's realistically the most important part of the job. I've been both, and I've had the pleasure of being a minor assistant on a high school staff that was stocked, top to bottom, with great former head coaches with incredible records who just wanted to do their thing. In that particular scenario, the head coach was possibly the worst of the lot at the X's and O's, but he was unflappable, positive, and genuine, and he held it all together. The OC was a genius, and he could gameplan anything. The DC kept things simple and woke up in the morning looking forward to seeing some collisions in tackling drills.
I absolutely agree that Bo should have remained a DC. When you find those types of coaches, you hire them and give them the autonomy to do whatever they want, and you try to keep them happy. It seems like a good DC is more likely to be willing to stay in that position, but it's rare to meet a top-flight OC who doesn't want to run the whole thing and still call plays. As an assistant I often couldn't wait to get my opportunity as a HC, but as a HC I often think about how nice it was to be an assistant under a great HC.
As for Saban, I think that posters here are selling him short. A man doesn't spend as much time at his level with this much success without valuing people. His assistants are incredibly loyal. Try to imagine another coach that Lane Kiffen, Kirby Smart, Mark D'Antonio, and company would all work for, admire, and have nothing negative to say about. There hasn't been another like him. Bobby Bowden used to say that the best head coaches are smart enough to recognize when another coach is better, and humble enough to hire them and give them space to succeed. Saban does that, and nobody has been better at it. Swinney might be in the same league, but he needs to stick around longer to prove it.
At the risk of stirring up a hornets' nest, I have to mention that Swinney is a deep and sincere man of faith, as is Scott Frost, Bobby Bowden, Tom Osborne, and an unbelievable other number of other wildly successful head coaches. This is a perspective that places premium value on relationships, hard work, striving for perfection, and forgiveness. Especially at the college and lower levels, this is what's often the foundation that everything else is built on. If you haven't heard him before, here's just an off-the-cuff example of Dabo talking about his faith: