Amazon has been very hit/miss lately, not just on physical music releases. It's possible a combination of their sheer size/bloat, push to maximize dwindling margin, alienating a percentage of the local work force (and trying to automate perhaps too much) with lousy jobs, and going to a primarily internal delivery infrastructure is finally catching up with them. Logistics at their scale is dizzying.
My order is still alive and scheduled for sometime early December. I'm not concerned there won't be copies for the coming months and I've retained a stereo version so I can enjoy the album while I wait. At this point I'm as curious to see if they actually fulfill the order as I am the opportunity to finally hear the surround mix.