I think player content is the future, but not in the manner of STO where players design shitty missions or pretend to be dungeon masters. The proper player content would be part of the world, such as a player owned keep, with rented guards and mercenaries, and a persons acquired loot guarded by a chained dragon or other earned or bought nasty. Thus, it's created by a player but not segregate from the world itself. Add 'guild' keeps, with groups, and throw in factions, the ability to sneak in, bounties, and a plethora of other 'player' focused things and you have a truly dynamic world that allows for politics, rare loot that changes hands, and an actual economy.I think player designed content could work if everything was voted on and then went through final approval by SOE. Give the players the tools to create content but only a very few things ever get chosen (best of the best). If the content you were working on didn't get picked then you go back, make it better, and try again. This would allow for quicker new content to players while SOE worked on larger content releases for the game. I think there are a ton of super talented people who could create some really great content for players.
I'm personally tired of lemming built MMOs consisting of churning through theme park McQuests over and over, as well as dailies, instanced PVP, and tired static raids.