Could be after the leap (suppose Jai is the one to vanish) he comes back to get a divorce from Bani because he wants to legitimize his son (authorities require a marriage certificate etc etc). But meeting Bani old feelings stir esp her closeness with Tarun brings out the jealousy in him. further to that he finds out that they have a child Krishna. Thus now he is in a quandary, which relationship to legitimize. Maybe that is what the promo relates to??
I am sure Bani will give him the divorce as she doesn't need his name for their child.
Then he will discover that pia's child is not his etc...the drama goes on