I think people would be unlikely to replay raid zones over and over to the degree they must play in many 2nd era MMOs. Usually the "gear chase" is tied to repetition of a raid instance in a 2nd era MMORPG.
Though if one could play the content perhaps once or twice to get all the story & content out of an instance I think many would be okay with raiding for it's own sake or simply minion rewards.
That heavy repetition of 2nd era raiding or the obscene time investment of 1st era raiding is major source of negativity. The cooperation angle in which one's success is so strongly tied to others is less so in GW2 than limited linear class based gameplay systems. Everyone is a self sufficient machine in Guild Wars 2. The nature of the combat does not lend itself to "LF Tank" or "healer drama!" and other such woes of getting 10 or 20 folks together.
I think it will be mostly okay.
Heck, I don't even know what the rewards are for the open world raids in GW2 now. I did them, just to do them, and there seemed to be a lot of other random people there too just for the heck of it. Not necessarily for the limited edition mini pet, new backpack skin or whatever other useless shit the game throws at you constantly.