Naruto:
Becomes Hokage, but is the protector of the village (and establishes relations) while Tsunade does all the paper work. (Much like the 4th and the 3rd)
Sasuke:
either dies, leads the hidden sound and becomes the leader of the small nations, or returns upon hearing Itachi's words from Naruto
I believe the next "threat" will be the smaller nations with The Land of Rice Patties (Hidden Sound Village) at it's head with a legion of Uchiha. During the Time Lapse, or possibly during the 3rd season if this would be the 4th, Sasuke learns of Itachi having children (I know sounds far-fetched but it's not out of Kishimotos league) and raises the child and has kids of his own. this starts the Uchiha legion. Sasuke gets the other small villages to train with him and smaller villages power greatly increases. This leads to the next great ninja war, after a time of "Peace"