Honestly, I would believe it if Sasuke just banged Karin just so she would shut the hell up and stop trying to seduce him. But really, if plot would have it that Sasuke did in fact have *** with anyone other than Sakura, I honestly want it to be hilarious but justified.
I can imagine Sakura stumbling upon a list that Sasuke keeps hidden, and she sees over a hundred girl's names listed with check marks next to them and she asks what they mean. Sasuke pulls out his phone or something (cause apparently NV has smartphones since ch. 700) and shows Sakura a picture for every name on the list, and in each one it shows him with that girl and like 1-3 children each then Sasuke explains how he has an obligation to restore the Uchiha clan and Sakura just stands there, speechless, and then BAM color failure and faints... again.
Then Naruto, who was also there, comments "I can't believe you did that... Single-handedly"
*Naruto and Sasuke fist bump and chapter ends*