Well, accourding to the messages they've been putting out the severly underestimated the amount of work they had left to do on the World guide. Whole sections had to be redone since they'd been written three years earlier. Artwork needed to be resolicited to for the new sections, and the city sections had "write three to five pages to cool stuff for X" as place holders. So things took longer.
I just wish they'd form a better grasp on these things so they could start pumping out material at a reliable pace fro us RPG geeks.