I know it's really premature to even bring this up and it is purely speculation based off of nothing more than something that, in my opinion, would be really cool. The Dreaming City has been a really cool experience and having a destination tied to the endgame is something Destiny was really missing prior to Forsaken. What if Bungie has been working to make The Leviathan an endgame destination for Penumbra? They have stated we wouldn't be going to any new location and technically this would still fit into that statement. The Leviathan is enormous and we have only seen a relatively small portion of it. I know it's not very likely but I think it would be a pretty cool addition.