He won't be released, ever
He will die in Pakistani jails from some chronic disease or long-term health problems, or he may get killed by some "patriotic" inmate, before the Case is decided. We were not going to hang him anyways.
As for ICJ jurisdiction, International Law is nothing but International Morality, and Morality is not "binding" in nature. It's entirely up to Pakistan to accept or reject ICJ's jurisdiction in matters related to our National Security. In my opinion, Pakistan should accept ICJ's jurisdiction as it (possibly) can set a precedent for how future India-Pakistan cases are decided.