It's a common practice in Mexico, there's a really just one chain of stores that sells CDs, DVDs and Blu Rays (although stores like Wal Mart and the like also have a smaller selection) called Mixup which is in pretty much every mexican mall.

Anyway Mixup stores put stuff out whenever they get it, last month they had some Superman Blu rays that were supposed to come out a week later, and there are tons of examples like that. I went to two different Mixup stores and both had it, several copies and actually one had Episode I playing. The official release is the 14th I think. I guess they don't care since they're a monopoly, and the stores are owned by the richest man in the world (Carlos Slim).