A recent patent filing has given us a look at a cover which MS considered for the Surface before ultimately going in a different direction.
According to the patent, Microsoft thought about augmenting the keyboard on the Surface's smartcover with an E-ink screen which could be changed to show different keyboard layouts or other controls.
Microsoft also noted:
Although many of the examples described herein relate to textual input by the user, the user controls need not relate to textual input. For example, the visually static user controls may comprise controls for a music / video player and the visually dynamic user controls may show thumbnails of album art (e.g. for the particular song or album or related / similar songs) or related videos. The visually dynamic user controls may in addition or alternatively comprise other, dynamic, controls for the music / video player such as a slider for scrolling through the track (where the visually static controls are the controls for stop, play, pause, skip, etc.). Similarly for gaming, the visually static user input controls may provide the standard user input functionality (e.g. left, right, jump) and the dynamic user input controls may provide user input functionality that is only available at certain points in the game or for which the visual representation changes frequently (e.g. where the control displays the number of lives or bullets that a user has left).
The patent was filed internationally in September 2016.
As a general rule, companies don't file patents on their products until after the product launches. Companies don't want anyone to steal their ideas and beat them to the market, so if you see a patent before the product it usually means that there won't be a product.
So if you threw out your $160 Surface Type Cover in anticipation of an E-ink replacement, go get it out of the trash and brush off the coffee grounds.
It isn't going to be replaced any time soon.