Indeed, people lost interest if you aren't showing new elements of gameplay, is like Call of duty every year or FIFA ( sports games)
every years is almost the same, so the people avoid some releases. The same here, yesterday I was showing an old image and a guy reacts impressive for the changes of 0 A.D since the last time he play the game.
another suggestion, keep feeding the people with new possible mechanics that can be released soon in the social network.
this helps to maintain the hype.