I am sure that Arohi won't marry KS. She has loved one & only one person in her life & that's Arjun. She has given Arjun that place in her life & heart which she won't be able to give anyone else.
Secondly, KS will never approach her seriously for marriage. This might just be his plan to take revenge from either Arjun(for his shot) or from Arohi(for slapping him).
I don't think that'll happen. He is KS & not Arjun. Wo Arohi ka 24/7 bhashan jhel nahi payega.
If Arohi & KS get married, then that will be the last day KMH will have positive TRPs. The next day itself, KMH will have negative TRPs.