A new Microsoft patent application has emerged that Redmond filed on May 1, 2017, but was only published by the U.S. Patent and Trademark Office on November 1, 2018. The patent application shows an interesting feature that might turn up on a future version of the Surface Pro. The feature is a second supplemental display on the back of the Surface device that Microsoft has dubbed a "reflective display" and it would sit right above the hinge for the kickstand on the back.
The abstract on the patent explains the screen would be a reflective multi-layer structure that forms an external surface of the electronic device and has a light-emitting display. The display portion is separated by a dielectric polarizing film and a diffuser from the surface of the computer. Microsoft gives us an idea what
Microsoft notes that users are demanding smaller and more powerful devices and that these devices must use components that have multiple purposes. It also notes that some devices have a surface area near a keyboard or touchpad that is unused, except as a wrist rest. The patent summary goes on to explain how the a pen stylus inking area on this display would work.
Essentially, the tech inside the metallic-toned, opaque external display can light up pixels where touched with a finger or a stylus (presumably the Surface Pen) and then sequentially transmit the light when the stylus or finger moves. It sounds as if the screen gives the effect of writing on a piece of paper so you can handwrite sentences and see all the words at the same time.
The display itself is metallic toned to match the metal on the back of the Surface Pro for a uniform look. Microsoft talks about scenarios where the same tech could be used in an external peripheral, integrated into household appliances, or incorporated into the surface of a desk. As with all patent applications, there is no guarantee that this tech will ever make it into a consumer product. Microsoft introduced the newest Surface Pro 6 in early October 2018, so we are likely at least another year away from seeing a new Surface Pro that might incorporate this reflective display embedded.