Sounds like a good thing, right? However according to the folks at Kotaku, it seems that during the month of September, Valve saw a drop of nearly 16% in active DotA 2 players. Based on the timing of the decline in players and the release of the DotA 2: Reborn update, it would seem that players might not have appreciated the update as much as Valve had hoped.
In some way this makes sense as there have been numerous complaints about bugs in the game, with several players claiming that the update made the game harder to interact with, and so on. However Kotaku speculates that it could be due to other reasons, such as school starting again in the fall, or that this lull could be due to The International DotA 2 competition ending, or another possibility is that there has yet to be an update to the gameplay that gamers can get on board with.
This seems to suggest that maybe players are getting a bit bored with the state of things and that Valve needs to shake things up a bit. In any case DotA 2 is still an incredibly popular game, but this drop in active players should definitely be something Valve needs to look at.