There is a whole lot of stupid on this forum page, and I hate to do anything to contribute to that.

But for what it is worth, "connected" neogaf posters-- folks that have revealed correct information of this sort in the past-- have heard that the delay relates to Wipeout HD failing epilepsy testing required for video game releases.

It's a bit of a read but you can find the discussion here:
http://www.neogaf.com/forum/showthread.php?t=327708

Emphasis: this is rumor and quite possibly incorrect. To me, it does make some sense. It would be a technical issue that has a nebulous solution-- providing an uncertain release date to a game that seems to be, by all accounts, essentially finished. Certainly Sony would be in no hurry to advertise the nature of the delay. Finally, having seen the "zone mode" vids for Wipeout HD, I could imagine there being some problems of this sort