there is a gate just east of outpost zimonja that's on the map border, you can open it but can't progress through it
2 large pipes leading off under the sea to the East, seems a possible hint of an underwater expansion.
There's also the old Abbey of the road from FO3 that's ment to be near here.
the Battle Zone & Robot Races seem like they are set-up for future content but, I could be wrong.
Maybe the underwater DLC could come with a purpose built underwater power armor suit. It could be like a submarine suit or something like that. Build it out of an ultra light and buoyant material, and it could contain foot mounted propellers.
I hope so. Those areas are massive disappointments - you had to kill everything that was there. But TBH, I hope BGS just patches them in with a couple sidequests and some radiant quests and doesn't center whole DLCs around them.
I want...not Enclave necessarily...but more pre-war lore/reveals. I want to know who Vault-Tec is and why they did the things they did. Poseidon plants in the Commonwealth are noted as are the events leading up to the Enclave and the Cali rig in Fo2 (check out the Boston Bugle terminals).
I like to think they're hinting at aquatic content.
-1/3 of the map is nearly empty.
-There's talk of a ghoul whale at bunker hill.
-Cut harpoon gun
-Mutated dolphins (some of which are interactive).