I've already positioned my character near the old iron king primal bonfire in anticipation of the second DLC.
People have been speculating that we will learn more about the past of the iron king, the downfall of the iron keep and the smelter demon, but I haven't seen any indication that the portals to the new areas contain any sort of time travelling?
As far as I'm concerned, the sunken king DLC took place concurrently to the main game. (Yes yes, I know time and space are warped things in the souls games
)