Depends on when Saban leaves.
If we are going to beat them while he's still there, then we have to get a lot more overall talent on the roster, have a mobile QB (when Saban loses, it's almost always to a team with a mobile QB) and catch them on a day when they don't play their best. Alabama doesn't lose often, but he's also only had one undefeated season.
Alabama will be a dominant force in college football for at least 2-3 years after Saban leaves. It's really interesting to think about how their decline will play out, but personally I think it'll go like this:
1. Saban retires.
2. The guy they bring in, whether it be Dabo or someone else, is good but not good enough. He struggles under the weight of the expectations. They go 3-4 years with only, say, one SEC title/playoff appearance, and no national titles. Perhaps they beat Auburn only twice in 4 years or once in 3 years. The new guy recruits pretty well, but they don't have the #1/2 class every year. Auburn and LSU are perceived to be rapidly closing the gap. Their fanbase, especially their younger fans who have never seen Alabama be anything other than the national favorite every year, becomes really despondent.
3. After a couple seasons of not winning the conference, the new guy is fired, despite warnings and lots of opinions from the talking heads that it is dangerous to fire a coach whose only problem is that he isn't as good as Saban.
4. The guy who replaces Saban's replacement ends up simply being not a good hire. This would be likely 3-4 years after Saban has retired, and any sheen he had on the program is largely faded away.