The casual user needs just one screen, our poll shows. There is interest in a second screen, but it cant be just anything ideally, the extra screen will be on the back and it will be eInk.
The reasons range from checking notification to preserving battery, eInk is great for reading long texts and showing an Always on Display at no power cost too. It does, however, preclude using the second screen for main camera selfies (the low frame rate will be a pain).
The Meizu Pro 7 was rumored to have an eInk screen, but it turned out that its an AMOLED. Theres YotaPhone, of course, but the company failed to gain traction. Its currently on the third generation, which should come out in the fall at $350-$450 or so (and with mid-range specs).
A second screen on the front (a la LG V20) proved to be the least popular option, followed closely by curved screens with Edge features. An Always on Display does what most people need, so there’s no need to overcomplicate the setup.
Flip phones inherently have two screens and Samsung occasionally makes one for China. The Galaxy X foldable phone could bring the next step large flexible screens that fold out of the way to fit in your pocket. Depending on how the screen folds, it could form two screens, however info on the X is quite apocryphal.
Will a return of the flip phone once the most popular form factor bring about a golden age of dual screens? All other form factors failed to do so.