I wonder if something went horribly wrong with the initial print run. It would not only explain the sudden delay, but it would be traditional.
Apparently, the original printing of the 1st Edition DMG had all sorts of problems as well.
I'm no fan of WotC's style of overpromise and underdeliver in the past, and I can see how this could be annoying, but I honestly am not upset about it.
I remember the 4e books smudging (the first run of em). Their response was to tell us gamers had greasy hands (and then later admit to the smudging).
If this, or any other issue, made the printing run unusable, that'd be plenty of reason to push back the release until they got reprinted quality books.
I just wish they were a bit more forthcoming with their reasons. I'd think people would find it much more reasonable if their reason was "our outsourced printer screwed up, we're getting 'em printed again, this time correctly, sorry for the delay." than "uhh, we're still formatting em." which makes me think they don't make getting their books out on time a priority.
I mean, I imagine if they said that about insider not coming out way back when "the outsourced design team dropped the ball and we basically have to start at square one" there would have been much less (not none, of course, but less) rage than "they're delayed".
But, as I said, (and as someone who is planning on getting these), in this case, I'm not upset.