It will be interesting if they decide to go with 24 people for their Adventure Zones. I'm one of those people who would prefer it being that high. I always preferred 25 mans over 10 mans back in WoW, and was happy that my guild stayed 25 man even when Cata came out. So was thinking it would have been around 12-20 players, but, again, I'm fine with 24.
Another thing that interested me in that interview was when he talked about the main quest and how you can just ignore it and come back to it later. I'm wondering if the main story levels with you. So if I'm level 15 and on, let's say, the 10th quest of the main story, but I want to put it on hold and decide to do it again at level 22 it would obviously scale up to my level. I really hope this is how they do it, because it would be nice to never be able to overpower the main story by just putting it on hold and then powering through it once you hit level 50.