Good post Laila2009.
I was thinking the same thing myself. But my gut feeling is that Asad would not want nikhat to marry a guy like imraan... Honor is very important to him. In fact if the engagement to tanveer is because of the pregnancy it will in fact also be to protect tanveer's honor that he would choose to marry her.
Regardless I think he will be tricked by tanveer into marrying her while she keeps her paak and pavitra image and in fact it will be the fact that she hides it/tricks him that will make him break it off---at least that's what the last epi indicates... Of course the CVs have surprised us many times.
Also I just don't want nikhat marrying that spineless creep anymore nor have anything to do with haseena bi... She will taunt and torture nikhat endlessly and make kachumber out of her.