Interesting thread 
I actually think the gap is going to widen.
Why? Custom hardware.
Not sure if you have been following Apple recently, but they have been adding more and more custom hardware to their platform/s, quite deliberately, I imagine, to increasingly separate them from everything else out there. I think they said their cameras can now make 1 trillion calculations per second, and they demoed some really cool ‘computational photography’. They now have a dedicated chip for machine learning, which can now do ‘live’ machine learning (on the fly). Much of those abilities and hardware can be tapped into by developers. The kind of apps possible on such devices are becoming less likely to be seen on your standard PC.
So I think we’re going to see a split - apps suited to ‘browsers’ and others suited to custom hardware within devices like iPhones and iPads. It just happens that, imo, a significant proportion of apps suited to browsers are exactly the kind that will benefit from technologies like Drab and LiveView (and the great thing for us, is Elixir and Phoenix can power the backends for all those other apps too).
Why do we have to choose? Each has their benefits, and I can’t see either dying anytime soon tbh.
