Previous Dark Souls DLC have required you to complete “about half the game”, and then generally warp you off somewhere. There’s not really a lot of dead space on the map for adding to it. I’m expecting something like a new object in the battlefield outside Leyndell, which when you examine it turns out to be Miquella’s memories and warps you off to another region to play through them.

DS1 and 2 required you to fetch an object and take it somewhere to access the DLC; DS3 just needed you to get to the right place. I’m expecting the ‘right place’ thing to continue. ER did have the three special blue daggers for the bell towers, so they might do a fetch quest, never know.