According to Sammobile, Samsung is working on an "Edge" version of the Galaxy S6 flagship, one which will feature a curved display on both sides. The functionality is expected to be inspired by last year's Samsung Galaxy Note Edge, a phablet with a single curved edge on the right side.
http://www.notebookcheck.net/Samsung-Galaxy-S6-Edge-to-come-with-dual-curved-edges.134798.0.html