@Ratty I have more or less same predictions like you. Coming to Dev yes I agree to you. To be frank he has already fallen for Durga. He has started seeing Nithya in Durga which he doesn't want to admit. He never liked Shaurya with Durga.
He simply does not want to acknowledge is true feelings for Durga lest his love for Nithya be questioned.
Durga on the other hand feels Dev can never love her. He loves Nithya the way she was. According to me most probably Dev will understand from lawyer the way Sakshi played the game, he will understand Durga is playing the game on behalf of Nithya and decide to help her as a friend. So in this war most probably they will move only as friends. That's why Nithya's b'day is kept.
Somewhere along the journey Dev will realize he loves Durga and cannot go without her, Durga/Nithya who is not yet madly in love with Dev would have fallen for him and will be worried whether he will leave her if he knows her true identity. So most probably we will be getting 2 guilt ridden people on Nithya's b'day.
Dev feeling he has betrayed Nithya by falling for Durga and Durga feeling she has betrayed Dev by hiding her identity.