it isn't in the store yet, but the store can update any time.
to stay informed just go to
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its their original blog, they'll post all the latest news on the homepage.
i am european and i'd have to wait 1 more day, otherwise i was playing this whole night
EDIT: The Dragonborn DLC is out!! Enjoy people! i wish i could already play it! this is what the blog says:
Wait is over! If you visit PSN and search “Skyrim” you’ll be able to find Dragonborn!