Odds of Hanging On
If you coach a popular sport, then once you're in, you're in. Even if you get fired as a college or professional sports coach because of a losing season, another team will most likely be willing to take you on in some kind of coaching or consulting capacity. If you have a talent for sports analysis and commentary, you might also be able to find a gig on broadcast television or radio.
Just don't abuse any kids while you're a coach. Not only will you burn in the hot place for all time, but you can kiss your career goodbye.
Also, beware the supposed depredations of Title IX. This law, passed in 1972, matters in college sports because it forces colleges to ensure that male and female participation in school sports is proportional to the number of men and women in the student body.
The problem today is that universities want to protect their spending on sports like football and men's basketball, which can bring tens of millions of dollars a year into a school's revenue stream. In order to avoid a Title IX infraction, schools will cut less popular men's sports like rowing and soccer for "budgetary reasons" and, if the schools think they can get away with it, they'll cut the corresponding women's teams, too.
This means, if you're coaching lacrosse or golf, your sports program will likely be the first on a college's money-saving chopping block. Keep your résumé updated and always have a back-up plan.