Well it's not concrete info, but it's a highly suggestive implication that canals are in. Via Pete Murray. Didn't know if it was worth its own thread.
https://m.reddit.com/r/civ/comments/4ktzoa/civ_vii_list_of_demands/d3i5o3w
This definately could mean something.
Making canal-cities has been a fan-favorite thing in Civ 5, maybe we would get a proper and more useful canal into Civ 6! Sure hope so..