I don't really think anyone knows even internally. Hop told us there was a meeting with Demoulin last week, but he didn't really go into details, which was probably no accident.
My prediction is they'll brighten up the black uniform kind of like how Bluecoats did after '13 to better highlight their movement. Maybe a white plume, white visor and accents on the shako, white gloves and a brighter cummerbund+dropsash. I remember thinking to myself the cummerbunds might as well have not been there from a distance last year because they blended in so much. A white stripe down the pantlegs could also bring back some of the lost motion from a distance. I can't imagine anyone would mess with the traditional formula, though. Now THAT'D be disappointing. Otherwise meh ¯\_(ツ)_/¯. The black jackets are still unmistakeable and quite good looking.