Yep, Bloodlance is just going to confuse people if he keeps using the word "Adventure Zone" like he is doing. I don't really care if you are using "parenthesis" around the word Blood, it is still confusing to people who don't know the difference between Adventure Zones and 50+(+) content.
Anyways, on topic, 50+(+) content is going to have the EXACT same quests as the alliances already have. They said a long time back when this feature was first released that it'll be explained because we are, "seeing through the enemies eyes." I'm sure they will make up some silly story that they are sending us over to the other factions area disguised as them and that we must complete any task we are told to do, even if it means killing our own people, so we can gain their trust and learn valuable information about them.
On the discussion on what the 50+(+) will be like, Maria Aliprando said that 50+ all the monsters/quests are going to be scaled up to about level 52-53, meaning they are going to be tougher than normal 50 mobs/quests making it a very challenging experience for people who want to do it still solo. It'll be possible to do it solo, but some missions might require some help. Then she talked about the 50++ zones being leveled around 53-54 being really hard for the solo player. It seemed like she was saying this part will require you to group up with another person a lot of the time to be able to complete a lot of quests since the mobs will be a lot harder for you to kill on you own, unless you are a godly character. And since the entire zones are all the same level you can start anywhere in the zones you want and complete quests how you want since the levels will be staying constant, compared to when you leveled in your own zones.