Nothing really new. They described very well the gameplay changes in the official websites and in an E3 interview. But since they struggle to send their messages and in-depth infos, I think it's good to explain and re-explain to people.
When they showed AC3 parkour between 2 sequences of AC:Unity, well, you can notice the gap between the 2 gen... Clipping, citizen-less, small and flat buildings (and large avenues, which reduces the density), flat lighting, eveyrhint less detailed... 2 years ago it looked amazing to me (and even today on a gamepad it looks not so bad (but my fullHD TV it looks terrible)). Even Black Flag on PS4 isn't that beautiful.
They are really targeting what the players wanted since AC:Revelations in terms of overhauling of the general game design / game mechanics. I don't know if they could have done that before, 1, 2, 3 years ago, but it will definitely enable the next-gen AC games to have a less flawed and constrained basis, especially since they tried to make a "pure" Assassin game such as AC1. They have a game design view really close to AC1 and far from the Ezio triology and the Kenway games (2, 3 counting Rogue), which developed the gameplay and especially combat, along with tricky little stealth mechanics... something that was heavily criticized among core gamers (hello gaf)
I hope we'll see more gameplay at gamescom