Here's a quote: "The humans are the most well known race to our players, but they're also the ones who have suffered the most changes. Ascalon has been taken by the charr. Elona and Cantha are lost, unreachable, and Lion's Arch is no longer beholden to the human throne. Only the nation of Kryta, led by its Queen Jennah, stands as a bastion of human civilization. Their last great city, Divinity's Reach, shelters humanity from total destruction. They still worship the Six Gods, but the human gods are less active in the world, perhaps reflecting the decline of their followers."
http://www.last.fm/user/walladude2 New York Mets: 50-55: There's Always Next Year
I didn't read the IGN interview yet to see if it was explained, but the movement of the world article explains this. The reason Cantha is cut off is because of Orr rising from the sea... No one can get around to the other side. Same thing in the Crystal Desert. Another dragon and his minions (as well as Palawa Joko) are cutting off access to Elona. So no, we don't have access to those areas... yet, but more than likely new games with come out with the ability to get there.