I'm very thankful for the advances that medical science has made during my lifetime. Without them, I seriously doubt if I'd still be alive - and the same is true for many who are reading this. God has made these advances possible, and we should thank Him for all His mercies - including these.
I recall reading an article by a noted medical researcher many years ago on this question, who wrote that he seriously doubted if it could ever happen. For one thing, he said, almost as soon as one terrible disease is conquered, another takes its place. Nature seems to be against us, he stated, and pointed to the recently-discovered HIV virus that was just beginning its lethal march. In addition, he pointed out, the longer we live, the greater chance we have of experiencing a fatal accident.
Why is death inevitable, even if medical science does extend our lifespan? The Bible gives us the reason: The human race has rebelled against God - and death is the result. As the Bible says, "The wages of sin is death" (Romans 6:23). Eventually this life will end for every one of us: "Man is destined to die once, and after that to face judgment" (Hebrews 9:27).
But death is not the end! The Bible says we will live forever - either separated from God in the place the Bible calls hell, or in heaven with God forever. Don't gamble with your eternal salvation, but by faith commit your life to Christ today.