Possibility A: Arnav comes to know that Shyam is having an affair or lusting after some girl but doesn't know it is Khushi and so will try to investigate and find out more about this "girl" which can stretch the track for a few more weeks (post Valentine) before all hell breaks loose.
Possibility B: Arnav comes to know before the Saath pheras that Shyam is having an affair and confronts him after which maybe Shyam will poison his mind saying that Khushi was after Shyam and when he rejected her by breaking the engagement she is now trying to rope Arnav in her jaal. So Arnav will make a deal to marry Khushi so as to protect his sister's marriage and Khushi will agree because otherwise Arnav will break Payash's shaadi. I see possibility B happening because they seem to have completed all the premarriage rituals.
What do you guys think. I just hope they hold it off until Valentine and we get to see some sweet Arshi romance.