The problem seems to be across all types of tires.
I talked to my local automotive tire guy (decades of experience), and he said it is due to low demand over the last two years. It seems people really cut back on tires (either not driving, or driving them till the threads show), leaving tire manufacturers with too much inventory rotting away on the shelves. This year, they decided to drastically cut production, and now people want tires (go figure). My car tires were backordered "indefinatley" at the local shop, and 2-weeks on Tire Rack (I guess the big guys get priority). When faced with long back orders for my dual sport, I ended up buying a mismatched set of third and fourth choice tires.
If you can wait a month or so, placing your back order with a huge retailer will likely get you the fastest results.