What number comes after the Godaime Hokage?
As we now know, Danzo was only considered to be a temporary Sixth Hokage (Rokudaime).

 After the Fourth Shinobi World War, Kakashi becomes Konoha's Sixth Hokage (Rokudaime Hokage)
 

Whereas:

 Several years later, Kakashi decided to step down and selected Naruto to be the Seventh Hokage, thus making him the Nanadaime Hokage