Unfortunately, my alma mater has a very poor track record in highly-publicized intellectual property snits. Even when they have (sort of) prevailed, they have often been public relations disasters and/or the University ended up looking like a bully.
And yes, failure to defend your trademark can absolutely result in your being estopped from pursuing infringers at some point.
But I'm betting that the University can more than show that it is diligent just from its efforts pursuing those selling unlicensed and/or counterfeit goods that are actually referencing with the University of Alabama or its athletics programs.