I wonder if its 150+ hand crafted dungeons and an additional 100 or so procedurally generated small dungeons to bring the total figure to the 250+ we've heard about more recently.
I'd be inclined to believe him more this time around, since he has at least 8 people crafting them this time, as opposed to the one he had before.
Since the dungeon design team is solely responsible for that aspect of the game, I'd bet they'll be designing right up until shortly before it goes gold. It would make sense for them to focus on the most critical and complicated ones first, and then do the little filler ones last, since they're the least likely to introduce bugs.