These leaked screenshots do point to a slightly revamped TouchWiz UI, and one of the more notable features would be additional white space. The existing batch of screenshots show off the setting toggles in the notification panel that some of us might find it to be a refreshing change, where it sports a grey background with a shade of blue.
Apart from that, new information on the update’s release remains scant, although there is an alleged Samsung Marshmallow update roadmap that points to Galaxy S6 receiving the Android 6.0 Marshmallow some time in the early part of next year, in addition to the Galaxy S6 Edge, of course. As usual, this will remain a rumor until Samsung steps forward and makes it official.