Obviously I'm skeptical that this is real at all, since Aizen himself could have lied about the secret to stop his shikai, but if so this is all sorts of WHAT THE HELL DID THAT JUST HAPPEN AM I DREAMING. If he does die the only terrible thing I can think of is that we never saw Aizen's bankai, but this just makes Gin's even better since it's pretty much the best thing for an assassination(I'm sure Soi Fong wishes she had it over her current one for that purpose, only 1 stab needed instead of 2).
I'm still gonna wait a week though cause I don't trust Kubo, he's lied to me before.