This could theoretically be done with stemcell stuff, but it's not there yet. However, when we finally reach the point where we can infinitely regenerate our body cells, we'll become effectively "ammortal"; unable to die due to natural causes (such as illness), but we will still die from other people (for example, a bullet to the head)
Besides that, I think nuclear fusion would be an incredible development if we can finally harness it to power our homes.
Fusion won't be the silver bullet people tout it as for much of the same reasons as fission isn't (mostly politics). No politician wants to spend billions of dollars on something that is going to take a decade to even be functional and another decade to break even. It would get cheaper with scale, but so would fission, we just never let it get there. It also still produces radioactive waste, despite what proponents claim, and it even produces more radioactive waste than a fission reactor by volume. But it isn't as long-lived.
These are the same tired arguments we hear about fission. If your country isn't actively building fission, it's probably not going to build fusion, aside from demonstrations.