Guys, it's a really slow-evolving item. It's got TWO birthday cake poses worked inside of the item, so that should give you an idea of how quickly it evolves. sweatdrop Just enjoy the fact that you have the item. If you really need one of the other poses that badly, then quest up for the first generation one, that will have all of them.
And, since I'm still not sure if everyone here is clear on this: it's not finished yet. Perhaps the next time your 11th Pietro will evolve will be the next time the item series evolves.
And hey, at least you're not staring off into the abyss of the unknown. xD I can't imagine what it was like for those poor 1st generation Pietro owners who had to wait over two years to get the poses they have now.