cRPG isn't dying. Sure, Chivalry is an other game in the genre that doesn't suck major ballsack, and Chiv is more mainstream in that it's faster, more brutal and easier to get decent in than M&B. However, M&B/cRPG is a more complete medieval combat game, which is also more strategy based than others in the genre. Also remember that the ones still left in the game, are some very good players. Most of the people help to create a great community. A very big amount of the players are in clans, compared to other multiplayer games.
To conclude, I'd say that cRPG is a mod for a game that was never really that "famous". However, very many players who play M&B (whatever mods they like) stay with the game for a long time. I'm guessing when Bannerlord is out, very many cRPG players will move over, but perhaps we will get a Bannerlord cRPG? or perhaps people will come back to cRPG while waiting for a mod like that.
I would not worry for the cRPG fanbase, it may be small, but it is hard as steel.