Naruto Gaiden: Chapter 2 Spoilers:

[UchihasRightfulHeir]

Actually Tsunade would make more sense, and Orochiamru had the opportunity to collect her DNA and every. Orochimaru isn't the type to settle he wants the best.

Tsunade also wouldn't make sense. While she is hashirama's blood, she doesn't have his instant healing ability. That's why she created the byakugo. Like sakura, her healing comes from hard work. Karin is the only viable option.

 

[BlueMeteor]

Can't wait to see

 

[Kishi Uzumaki]

If Orichimaru is involved anything can happen even making Sasuke's genes infected with Karin's genes ( ofc may look over imaginative ) is possible but still i think Sarada's real mother is Sakura and if I'm right, Kishimoto is trying to make this interesting with all these mysteries .