ArcheAge's endgame? 2P has published a partial look at it in the form of a level 50 leviathan raid. Unlike most MMO raids, though, this one features seven phases of PvE action followed by a PvP portion that pits pirate players vs. non-pirate players for the right to claim the beast's body.
It's worth noting that 2P's information comes from the Chinese version of ArcheAge. You can watch a Chinese-language trailer featuring the leviathan after the break.