Well, one problem is that longevity may not mean youth at all. Increasing longevity may simply mean getting (and looking/feeling) older and older.
Even if we perfect the art of 3d printing new body parts and using gene-targetted cancer treatment, that may not make you spry, less forgetful, or less wrinkly
Biology isn't the only way to remove wrinkles. Our nervous system isn't very good at interfacing with electronics, but technologists will find a reliable way some day.
Even if we perfect the art of 3d printing new body parts and using gene-targetted cancer treatment, that may not make you spry, less forgetful, or less wrinkly