I think if you look at player numbers you have to put them into perspective with other games as well. Of course the numbers go up a bit when more people have time to play and they go down when fewer people do so. I usually check this page:
steamcharts.com
CIv7 for the last months has regularly been found between number 151 and 175, though at this time of writing it is down to 183. It seems it has found its bottom there and is unlikely to drop fast. If there are improvements to the game it might jump but if it stays like it is now it will only be a slow way down. If beeing the, let's say, 160th most played game after half a year is a success, I do not really know. It does not sound like it, especially as the two predecessor are always ranked way above. But if the people that play it pay enough money even a lower number of players might keep the game alive.
Steam Charts - Tracking What's Played
An ongoing analysis of Steam's player numbers, seeing what's been played the most.