Well i agree Sakura is the mother by law but nothin suggest that she is biological mother :lol
We all know that Karin hate Suigetsu and she has been lying to him since day 1
Second, for having Sakura chasing a forsaken criminal (who has almost 0 interest in her) in the forest just to get F with him is kinda retard, no normal human even think about it.
Third, the time that Sasuke stay in the village is so short that if he's gonna spend the time he walks out of the village to have s3x then leave is kinda awkward and insult to a human being (if Sakura even a human being...)