#3. To eventually turn on Roman Reigns
What's clear in the entire Erick Rowan-Roman Reigns attacker storyline is that we're going to be getting an alliance between two top stars in Reigns and Daniel Bryan. When they met in the past, they clashed heads, but for the first time, they'll be properly aligning together as a tag team (we're not counting Bryan's alliance with The Shield) and it's going to lead to a huge tag team match at WWE Hell in a Cell 2019.
If WWE is planning an alliance between Reigns and Bryan, it's possible that they could play it out on SmackDown over the next few months even after being done with Rowan and Harper. Obviously, the objective would be to go over them, but once that story is done, fans are obviously going to hope that the payoff would be Reigns vs Bryan and not Reigns vs Rowan again.
It could result in a proper heel turn and another incredible run for the New Daniel Bryan.