Mod isn't dead at all. I would give it at least 2 more years (except there's a new groundbreaking and better game replacing everything crpg has to offer but maybe not even then...).
Probably it will go this way: After a large player base is gone and improvements can't compensate it, there will still be a small player base left, that will even even more firm then the player base is now. Also those who "quit" will play from time to time, leaving a steady player base for a longer time. Well and if nothing groundbreaking happens the decline of players will only go forward very slowly. This at least is my prediction/experience.