CFB, like all amateur and professional athletics, is cyclical. It's impossible for a program to consistently achieve the level of success that Bama has had under Saban. But I think the biggest issues with that program is the lack of continuity with the staff, and the current crop of assistants, while good recruiters have not been very good coaches. Clemson beating the doors off Bama exposed a number of cracks in the foundation.
That said, a "dropoff" for Bama may be going 11-1 or 10-2 instead of 12-0. I don't think the wheels are going to fall off overnight.