>"The new story can also be played without even completing the original story first, but it would be more enjoyable if players have finished it."
No proto-sequel confirmed. Must be some side quest.
At least given the great job they did with quests in this game I'm expecting some more good stuff with the DLC. Also new blades to farm and rage over (I'm just 3 blades away from completing it, but farming is taking a toll on my sanity).