Is there any truth to the belief that when Moshiach comes, people will live forever and death will be eradicated?
A verse in the book of Isaiah states: "Death will be swallowed up forever, and G-d will wipe the tears off every face." A similar statement is found in the Midrash: "In this world, because of the evil inclination, our days are shortened. In the future, however, death will be swallowed up forever."
Among the commentators on the Bible, Maimonides has an unusual interpretation. He says that the verse of Isaiah is not necessarily to be taken literally: "It is inevitable that a person will die and return to that from which he was formed." He does agree that in the Messianic era, "man's life will be lengthened" and death will be considerably delayed, but in his opinion, everyone will eventually die. According to his theory, even "Moshiach will die, and his son will rule after him, and then his grandson."
In general, the view of Maimonides is that the ultimate perfection of the world will not occur in the days of Moshiach. According to him, after the era of Moshiach we will eventually return to the Garden of Eden, where souls will be stripped of their bodies and will experience the ultimate of spiritual bliss.
However, the majority of commentators reject the view of Maimonides. Chief amongst them is Nachmanides, together with many leading Kabbalistic and Chassidic masters. According to their view, the ultimate perfection will be in the days of Moshiach, when all souls will descend from the Garden of Eden and will return to be enclothed in bodies. Death will vanish completely and all of us, with Moshiach at the lead, will live forever.
(Isaiah 25:8. Midrash Tanchuma, parshas Yisro. Shabbos 152:2. Maimonides' commentary on the Mishna, Sanhedrin 10. Iggeret Techiyat Hameitim of Maimonides. Shaar Hagemul. Derech Mitzvotecha, Mitzvat Tzitzit. Torat Menachem 5748, vol. 2, p. 273. 5752, vol. 1, p. 186)