Oh no it's not
Apologies if I repeat something already pointed out but I haven't time to read nearly 100 comments.
I say "Oh not it's not" because I personally believe that smartphone sales are running out of steam because the damn things all look alike and are now showing only incremental, and arguably peripheral and unnecessary, improvements. Manufacturers followed Apple like perfectly cretinous lemmings with the candy-bar design and it is about to become a dead end. There's only so much tweaking of cameras and bezels you can do before folks ask themselves why on earth they should pay £1k for a phone that's hard to distinguish from the previous two models, which did everything that was needed already? Where's the innovation? Where's the dramatic new functionality/display tech/battery life?
Samsung made a couple of rather feeble attempts to break loose of this lamebrain follow-the-fashion design with smart flip phones (one was "Hennessy" I think?) but they were half hearted.
The screen is (a) the most important part of a smartphone and (b) the most vulnerable and (c) frequently most expensive to fix. We've had 10 years of sheer stupidity putting the screen all over the outside of the phone ... and millions of expensively shattered screens. And phones whose physical size was driven exclusively by the desired screen size; resulting in some offensively oversized models.
Considering we already had the example of highly successful flip-dumb-phones it is staggering that manufacturers and consumers were dumb enough not to see the obvious—hypnotised, I supposed, by Apple?
Therefore I suggest that we are about to see a new (old) paradigm: flip/clam powerful smartphones with two internal screens taking advantage of tiny bezels to perform as two screens; or one bigger one; or a screen plus (decent sized) soft keyboard; or whatever the software will allow. Externally a supplementary, well-protected screen does routine work for caller ID, app warnings, brief messages, notifications etc: perhaps an e-ink type of display, lasting ages and always on. At last we'll have bigger screens, yet in the same 4—6 inch size range for the unit. At last the expensive, nice display tech is protected from coins, keys, scratches and drops. At last you can choose to answer by flipping open, or not; to end a call by flipping closed, if you like.
The new possibilities opened up by combining smartphone power and display tech with the clamshell form factor will, I respectfully submit, rejuvenate an ailing marketplace.
We may not quite reach Westworld super-expandy-screens just yet, but hi-res almost-bezel-less tech can now do some remarkable things—and it's time for those with deep pockets and imagination to get cracking.