The correct option would be Nobody’s
In this case, the IS contraction is used and so the meaning of the sentences does not change. it is still expressing a future reference.
it is important not to get confused with the possessives (´s) otherwise this sentences would not have a clear meaning e.g Nobadys´.
Nobodys´s and nobodys are not grammatically correct options. so they should be discarded at once.
