Released perhaps with the Redstone 3 update in early Fall 2017, the NEON update will bring new design elements in play. Cassim Ketfi at Numerama.com has called it even "Metro 2," which is to say that it'll bring smoother transitions and more motion in the rather flat UI.
One can only hope that there's been a lot of development if Metro indeed would be the starting point, as it brought a lot of grief for Windows 8 users. Thankfully sources tell that the update has been in the works for over a year and thus doesn't seem like Microsoft would just backpedal to Metro.
There's still plenty of time until the rumored update will see the light of the day officially but you can be sure to see more leaks about this one in the upcoming six months.