Board Thread:Theories and Speculation/@comment-29769110-20161017201027/@comment-27973430-20161017202233

Sarada is not the daughter of Karin for one, being the descendant of both the Uchiha and Senju/Uzumaki doesn't mean one would definitely be born with a Rinnegan, and Sasuke having the Rinnegan does not mean his child would have one as well since Hagoromo's children didn't.