I say, and with God's success: He is obligated to make up the fast if he is able to do so. If he is unable due to his illness being connected to death, such that he did not recover from the illness and could not fast, then his illness is considered ongoing, and he is not required to pay the expiation or compensation. If he recovers for a few days before his death and then dies, he is required to provide compensation for each day he fasted, which is feeding a poor person, at a rate of two dinars. And God knows best.