We don't know much about the PVE endgame right now, other than it's supposed to be the same as what you've played from level 1; they don't pull the rug out from under you with a new game type like raiding.
There will be aesthetic gear to hunt down, like Legendary Weapons which are more than just run-of-the-mill models. One will turn your character to liquid metal, leaving droplets in your wake. Another is a bow that shoots rainbows. There are actually two greatswords, one that looks like Night and one that looks like Day (literally; the way they described them, looking through the model looks like a window) that can be combined somehow to form one super-sword.
We do know you can do sPVP and WvW to your heart's content (considering you're fighting humans who can always behave differently, they shouldn't ever get boring).
On top of that, ArenaNet has said that when the game goes live, they consider it a Service rather than a game; half of the development team will work on future expansions while the other half is the "live team" that works on adding lots of smaller stuff over time; new zones, dynamic events, dungeons, etc. Because of the de-leveling system, anything they add, even low-level stuff, is worth doing regardless of level, and will still offer you rewards and a challenge.
They've said "We want people to say that there is no game that gets better support than Guild Wars 2"... those are pretty strong words from a developer.
(You can hear more here, there are some audio issues but they fix quickly:
http://www.youtube.com/watch?v=IIExN1GZK_Q)
So yeah, that could've been the problem causing my fps to dip.
