And she will confront him. That is what the wedding sequence is about, to open the wounds that were inflicted at their wedding day again. I think there might be some problem with preeto's marriage as well which would make Arnav understand what Khushi feels towards the sanctity of marriage and how he shattered her dreams that day.
Perhaps his regret has already started today with the realization of what he did to the innocent heart of a young girl. Perhaps, we don't have to wait until Shaym's truth comes out in front of him.