Aren't completely dead, yet, but the move from InnoGames is clear, they will move the FoE community in one place from which all CMs and Admins can check everyone of them in one single place rather than on separate forum websites.
This trend isn't done only by InnoGames, there are many games that use discord as general forums, bug reporting system and many more. Discord is a huge platform, especially for games and gamers.
Personally I prefer discord, not because of FoE and their games, but for the multiple groups and other games that I have there. It's easier to access all of them from one place rather than having multiple accounts on multiple websites for the same purpose.