I'm not a fan of constantly hiring and firing coaches, I believe it can take time for a new coach to settle in and have things running optimally.
With that said, going from 12 to 8 to 6 wins is not a good trend. I would understand if there was a big dropoff in talent, but there hasn't been. We've had consistently great recruiting classes over the years, and we haven't had an above average number of injuries or underclassmen playing. We have, however, had a team that rarely seems to play 100% focused for an entire game. If the trend does not reverse this year then it's easy to believe that 2013 was a fluke and Gus is a 6-8 win coach. I hope the opposite of that is true.
I think any coach at Auburn needs to average 9-10 wins a year to have a long career on the plains. If Gus can have a 9-10 win season, his average will be fine and so will he. If not, I'd be surprised if JJ gives Gus a fifth year.