Well EQ didnt have encounter locking either, and they've not said a word about loot in that regard.
I doubt they go EQs way there (do more damage to loot), but that doesnt mean GW2 either (although I could live with GW2). Might be loot is randomly given to anyone contributing past a threshold instead of the one with most dps. Might be the initiating party gets any "special" loot while all participants can get xp, vendor shit, coin and craft stuff.
I do dislike mobs locking to the first person to hit them like in WoW, TOR (and EQ2?). I like the GW2 system of people being encouraged to assist each other on the fly. Now GW2 didnt have a good loot system (to go along with them not having any good loot) so they have to figure something out in that regard, but it's an area that can be improved.