Then why the unsealing?
I would find it strange to if Sora is a jinchuuriki, owuldn't be the brightest thing to do for a filler. But if you look all the facts...

Hateful eyes from bystanders
Usage of an unsealing jutsu similar like Naruto's
Responds to the Kyuubi inside Naruto
Ow yeah, the big ass monster hand we saw but that on a side note