What if:

- Before Itachi died, he had left a legacy just in case Sasuke did fully turn evil and Naruto had to put him down.

- There was a survivor of the Uzumaki massacre who wanted revenge for his clan, and became the next main villain for the upcoming generation or even when Naruto finishes Madara and Obito.

- Tobi had been Izuna :D

- Jiraiya was still alive

- Sasuke and Naruto fused