GW2 Expansion 5 teaser
Okay, here me out...
This can't be a coincidence.
Not saying "we're going to pre-Searing Ascalon" or anything, after all the spot is already in-game technically, but the image choice had to be taking nostalgia into account.
EDIT: FOLLOW UP!
If this is true...
Istan in GW1 is internally referred to as "Delta". Now while some regions' internal names changed between the games (e.g., Ascalon became "Regrown" internally for GW2), I believe Kryta (Valley) held the same internal name for both games. Half of Istan is left unexplored still, and there is a bog there - Lahtenda Bog.
However, it's also possible that this time Delta is referring to the region north of Kryta - which has an actual delta connected to Janthir Bay.

















