LG always makes a new innovative design like LG V serious. LG will release new innovative Phone in this September 2017. A leaker Evan Blass leaks the original concepts of this phone should be a slide-out secondary display.
That images are mockups and not sure that LG makes Slide-out secondary display. The renders image says secondary screen puts under the Primary screen. This screen should be used for Shortcut Apps, Keyboard, Search, Camera controller and so more.