#1 The tag team division really doesn't need them anymore
Once upon a time, The New Day were front and center in the tag team division, and to be honest, they were the only credible act carrying the load of the division upon their shoulders. But since then, there are so many tag teams who've stepped up to the plate.
You have The Usos, The Hardyz, Roode and Gable, and the current RAW Tag Team Champions, Ryder and Hawkins to carry the division on their shoulders. To give The New Day another run with the titles may actually take the focus off some of the other teams in the current division.
It really doesn't make sense keeping them together at all unless The Undisputed ERA gets called up to the main roster. And even if they do get called up, Big E's injury may play spoilsport.
Hence, I'm convinced they'll be split up.