CNS is not a proponent of lateral moves for his coaches and I don't think that Kirby has anything to gain by going to LSU as a DC. The only way I see him taking that job is that he and CNS are at odds with each other and I haven't heard of anything of that nature that has happened.
I agree with Jamos. I think he stays at Alabama until he gets a HC position or until CNS wants a change. It would be a bold move if Kirby Smart is doing this on his own with very little to gain and a lot to lose.