I could see it becoming more accepted if/when mortality is no longer a given, with people being able to live about as long as they want aside from accidents.
I think assisted suicide should be an option for anyone after they've been assisted in examining alternatives.
After my dad had a stroke ~2 years ago he told us that if he didn't recover sufficiently he'd be fine with checking out of this world, and we likewise told him we wouldn't blame him for doing so. He's still working on moving forward, so I don't yet know how things will end up. He lived an adventurous life up to the point of the stroke, so at least he didn't leave much undone.
To any physically healthy person feeling unsatisfied with things, maybe getting a little closer to one's sense of life/death would help, via (safely managed) extreme sports or volunteering with hospice patients.