Bungie originally intended to have Old Chicago as a location in Destiny but they eventually scrapped the plans and we only had mentions of it from time to time. The next expansion might finally get it in all its swampy glory.
Old Chicago is often mentioned in Destiny universe even though it never appeared in any of the two games. Graviton Lance was originally found in Chicago and the city plays a major role in the game's lore. Namely, it was one of the production hubs for Clovis Bray but all of that went off-rails when Savathun invaded and conquered what now looks like a bunch of rubble in a swamp.
Furthermore, Exo Stranger/Elsie and Ada-1 have both referenced the city previously where the Guardians learned that there are seven Black Armory vaults in it.
On June 3, 2021, Bungie posted a regular TWAB that announced a few things and showcased a few others but one teaser caught everyone's eye. The teaser in question is the picture you see above - a Guardian standing in a swampy area. In essence, this could be any swamp on Earth but we are all leaning towards Old Chicago since the city has so much significance for the series.
It also aligns with Bungie's policy of vaulting content and then bringing it back at a later date. Considering that numerous Black Armory vaults are located in Old Chicago, it's highly possible we will get an activity that will have us reacquiring the gear Bungie took away with sunsetting.