Most people will just quit when the leveling gets insane.
Unlike EQ, where there is a very strong social aspect to keep people in the game AO has none of that so the peeps will just quit when the leveling gets too frustrating.
In my case I left EQ to come to AO because I can solo missions and even without the 14.x patches if I can't do that there is no sense in staying around.
My main hit level 53 as a Troll Shaman in EQ in May of 2001 and hung around doing quests, making twinks and fooling around till just last month, still at level 53. There is no way I would do that in AO there is just not enough other than killing stuff and leveling that would keep me here. If I can't do that I'm gone.
I'm so average that I'll bet this feeling is echoed many times by people not posting on this board.