The Old Blood will be a standalone prequel for The New Order. It will be $19.99 and launches on May 5th
It will have two parts (I'm assuming this means two levels) "Part one of Wolfenstein: The Old Blood - Rudi Jäger and the Den of Wolves -- pits BJ Blazkowicz against a maniacal prison warden as he breaks into Castle Wolfenstein in an attempt to steal the coordinates to General Deathshead’s compound.
In part two – The Dark Secrets of Helga Von Schabbs – our hero's search for the coordinates leads him to the city of Wulfburg where an obsessed Nazi archaeologist is exhuming mysterious artifacts that threaten to unleash a dark and ancient power."
Make sure you watch to the very end

Personally, I thoroughly enjoyed The New Order and always wondered why they never made DLC for it; it has really good FPS controls and satisfying weapons but the main game is too short once you know where to go and what to do.
I'm assuming Bethesda/Zenimax didn't know how well TNO would be received so they didn't plan on any DLC, but once it came out it, it was too far away from the game's launch to have this come out as simple DLC and so its standalone. I'm cool with that, because hopefully it means the file size will be a lot smaller.
Anyways, this looks rad.