I don't think we'll be seeing Harold in the game, seeing as he appeared in Fallout 3 and is not really in a condition to go anywhere at the time. Still, I could see this being an attempt to recycle the premise of the Nursery, after all, it would be a waste to just through out every concept conceived for Van Buren and do nothing with them.
Even if Harold was dead, immobile, or went to a different planet, doesn't mean he's exempt from being in the game. He doesn't have to physically be there to be there, ya dig?