If there's one thing that Prism Nana's third pilot has in common with the last promo, it's that both segments feature characters falling to their death. Therefore, my suspicious have yet to be magically destroyed.
For some odd reason, I am getting a bit of a Yukiko vibe from the new girl -- I think it's the kimono and scenery that she's in. But anyways, her special bow and arrow summon also reminds me of Mami's Unlimited Gun Works from Madoka Magica.
I am definitely enjoying how Shaft is introducing the girls of the series, since the red magical girl's element was shown by having her get fired up over helping her best friend build a rocket. Then the new girl shows off her element by expressing her love of nature. Based on this theory, this means that the blue magical girl is going to cool us off during the fourth pilot promo, and the last three will surprise us with Shaft's magic.
Shaft continues to remain silent about the Prism Nana project, but I think their announcement will come after all seven pilot promos have aired. So let's wait patiently, and enjoy every segment that Shaft throws at us.