No, looks at Warlords of Draenor, there's not enough content and people start leaving, not everyone interested doing all achievements or doing all quest. PVP and PVE are why people comeback to the game again and again, it's feel rewarded. You spend countless hours grinding, or looking for Proto Lost time drake, and leveling for reaching end game content like PVP or PVE, this is why Blizzard lower leveling difficulties so people can reach end game faster because the content of the game after expansion and expansion are in end game, Blizzard now focus on end game and ignore low content, yes I know this strategy doesn't work as supposed, but you know what I mean. After Ashran Failed they leave, Archomonde defeated more leaves, now WoD are Grindfest Apexis and rare mounts. You dont want lordaeron become Grindfest right?