#1 The Shield vs. The Wyatt Family
Even though WWE already did this feud back in 2014, I wouldn't be surprised to see them go back to it before the end of this year, simply due to the fact that Rowan is set to miss a significant amount of time due to injury, thus putting Harper in a spot where he might not have anything to do.
So here's my prediction: after The Shield takes care of Strowman, Ziggler, and McIntyre, WWE will move Harper to Raw, where he, Braun Strowman, and Bray Wyatt will reunite to take on Seth Rollins, Dean Ambrose, and Roman Reigns.
As we saw from their previous feud four years ago, these teams have incredible chemistry together. Furthermore, it'd be a good way to get Bray Wyatt back in the main event scene, and it'd be a good excuse to continue the Reigns vs. Strowman feud over the Universal Championship.