A patent application filed by Samsung may shine some light on its upcoming dual-screen phone. The patent shows the two displays being used in a manner similar to the Nintendo 3DS.
According to the patent drawing, the second screen can be configured as a virtual controller for the game running on the second screen above. Depending on the game running, the controls can be for 3D-space control or just a linear control scheme.
Stylus-based input control has also been included in the application; presumably involving the S-Pen. Additionally, the stylus would be useful for drawing apps as it can use the second screen as a drawing surface, while keeping the primary screen free for previews and magnification.
Notable in the patent filing is that the phone will have its own set of sensors and front camera on both screesns, not unlike the ZTE Axon M.
We know that the smartphone codenamed Galaxy X is set to appear sometime in 2018, but as for now we do not know when will the date be.