#3 The New Day breaks up
Although they are still hugely entertaining and over with the fans, the whole 'stale' nature of the tag team division on SmackDown has been due to the New Day, Usos and the Bar dominating and basically monopolizing the tag team division.
While a split would likely hurt Xavier Woods the most since Big E is the total package and Kofi Kingston is a highly respected veteran who is more than overdue for a main-event run, Woods' potential is unknown.
Split angles can do big business if done properly like the original split of the Shield or when Evolution turned on Randy Orton and then eventually ate itself.
The eventual split doesn't have to necessarily involve one member turning on the others, but it could be an amicable split should it be booked that way.
Factions don't last forever and in order to 'shake things up', a member of the faction might get drafted to one show while the others remain on a different show.
Mr. McMahon just might want to change things since the ratings haven't been where he wants them to be, so don't be surprised if the New Day sees its last year together as a faction in 2019.