He (Jonah) would have remained inside the fish until the time of resurrection (he would have remained in a state of corporeality until his time of death).
Sayyed Abbas Sadr-Ameli
He would have tarried in its belly until the Day of Resurrection
Al-muntakhab fi tafsir al-Qur'an al-Karim
He would have remained burried in that grave -the belly of the fish- till Resurrectio