Nobody will live forever. Even the mightiest of stars eventually come to an end. I do not fear what these people are doing. Like those who tried to build the tower of Babel, if Hashem wills it not to happen, it will not happen. People have tried to escape the limitations of physicality since our creation. But the physical world has limits, and time is a limit, and time limits all which exists in the physical world. Once Hashem began the process of creation time began, before this there was no time. Once time has begun there is cause and effect, and events in the past have lead to the reality which we live in today. All the fantasy in the world will not change the physical world. The constraint of time will always be a challenge. I do not fear the future at all because of this. As others have said, it is fine if it extends the life of a person, but to seek immortality is folly.