Filler Content Thread

I am one person, making an MMO. I see myself, in the future, having a difficult time keeping players engaged. There is a heavy focus on world PVP but I don't know if it'll be enough. I am looking for ideas, opinions, experiences, or whatever. How do you create filler content, without the feeling of procedural generation or that "Collect 10 Meats" quest? Is it even possible? I do like the idea of player content creation but that would probably push my release date back another six months.