In last days, some rumors about Hangouts by Google is in our hands. Hangouts will lose its SMS/MMS capability. This change will be very unpopular, of course. But this one will not be the only move. Others functionalities will be in Hangouts.
I have liked the SMS facility in Hangout. My conversations are more organized. To me, of course. But for some people, combining SMS and Hangout turns things confuse. Let's see what will be the reaction from the big audience.
Now, see a great improvement: Hangouts will get a fast reply capability from notifications section. We will write a message and send it without open any other app. Hangouts maybe would be your main message app.
Of course, all these points are rumors.