I don't see who SnapChat will lose to besides themselves (i.e. monetization). IMO Facebook/Instagram isn't well positioned win today's 13-25 demographic.
The point is, someone will win. And right now I'm not sure who else is in the running.
It honestly feels like Google is actively trying to sabotage themselves for messaging. I just don't get it.
I think duo is the right idea, where making a video call should be just as easy as making a phone call, but so far every time I've tried to use has been met with "install what? can't we just facetime?"
Yes, it's exactly that 'more difficult' I mean by 'you can't bundle them any more'. SMS and 'HoIP' with the same contact used to appear in the same conversation, but they removed the feature - disabling it for those with it enabled a priori, and disabling others from enabling it.
There is a big risk here though. Twitter has crashed and burned when compared to Facebook.