I'm wondering what's up with these, too. I found Pinkie Pie & Rarity at Target, Pinkie Pie didn't have that umbrella hat, and if I remember correctly, Rairty didn't have any new accessories either. I checked the copyright on the back of the boxes, and they were both 2010, whereas the copyright on Luna and Celestia were 2011. Maybe they're old stock that just got put out?
I have no idea if the Pinkie Pie FS re-release with that totally awesome hat is going to make it to stores, or if it was just a prototype. I'm holding out for it, but I might just buy her next time I see her, regardless the accessories.