It’s a possibility that are you marked is reserved space for future expansions. However, with the latest LS update, it looks like a split between the Mursaat and Primordus.
The area marked by the star seems to have a stretch of coastline and a lot of water, making me think if that area was used for future expansions, it would be the Deep Sea Dragon.
Going back to the previously mentioned, I think the next LS is going to include more areas being revealed in the Maguuma Jungle (Mursaat) or perhaps a trip across the sea to the Ring of Fire (Primordus). Okay, I’ll admit the bit about the Ring of Fire is probably just wishful thinking.
Stepping back to GW1 expansion, Eye of the North, Primordus was located in the deep subterranean levels of Tyria. My bet is that the future LS is going to build up with a chase further into the Maguuma Jungle after the Mursaat and it will eventually lead underground to where Primordus will most likely be fought.