There goes my Q4 2016: Civilization 6 is coming in October, with big changes.
In many ways, Civilization 6 takes its predecessors and iterates on the systems that have come before. There are changes being made to trade, research, religion and more. Based on the limited amount of information so far released, these changes seem to be incremental.
But there is also a big change coming. In previous Civ games, city improvements were mere statistical boosts or manufacturing gateways, rendered prettily with a slightly different artistic representation. You built a wall and your defenses improved and your city, quite clearly, became encircled by a wall. They lived within the city, outside your control.
Civilization 6 is not the same. It demands that you place your city improvements in geographic locations in hexes around the city, which best take advantage of that building's boosts and functions. This means that your city upgrade path is no longer a rote event. It is a matter of geographic practicality.