it's Thor's sister.
old Loki will probably trick Thor and trap him in the 10th realm,somehow his sister will come into Midgard to continue her brother's work,and protect what he loves most.
kinda like ms marvel becoming captain marvel,his sister will take his name to carry his legacy.
I am sure Thor(the real one)will be back by 2016 max.
@New_World_Order what are your thoughts on this?