Going on how the story develops, I think the writers are influenced by the current pop culture (Game of Thrones). While they adding new characters, and no one from them died yet, the destruction of Lion’s Arch and Kessex Hills was the twist that shocked everyone. Even if teasers about that event were released beforehand.
It would be ideal if Magus Falls/Manguuma stay permanently( and included to map completion if necessary), instead being instanced for the Living World S2. They can write the next set of story to a new area of Tyria(GW2) / also known as old maps of GW1 area. It would be quite interesting how those areas changed after 300 yrs.