This follows previous reports that Sony has wanted multiplayer in past Horizon games
Horizon MMO reportedly in the works at Guild Wars studio NCSoft
Horizon MMO Is Reportedly Being Developed by NCSoft
Sony announces Horizon Zero Dawn series in the works at Netflix
Sony is reportedly teaming up with NCSoft to develop a Horizon MMO
Horizon News
Sony reportedly developing Horizon MMO with NCSoft
Sony is working with NCSoft on a Horizon MMO, claims report - Neowin
Sony is working with NCSoft on a Horizon MMO, claims report - Neowin
Horizon: Zero Dawn MMO in reportedly in development - Video Games on Sports Illustrated