Tbh it's looking likely in the long run Splatoon could outsell FFXV in Japan but only if it remains PS4 exclusive, Splatoon in 6 months has entered the same ship as franchises like Smash, Monster Hunter and Mario Kart where it's a subculture in itself and these are the type of franchises that become rock solid in Japan and sell for years until the next installment. Considering how the game was written off by many to be another W101 it's crazy to now see this game heading to the 4m in 6 months.