By the time children today are old enough to die from natural causes, we'll have a cure for that.
At some point I think we will 'cure' cellular senescence. Then humans can stay physically in their prime, indefinitely. But there are other limits, like memory. Because memories require physical space, there is only room for a limited amount.
I think we can get past that either naturally, by overwriting old memories, or artificially, by augmenting memory with technology. Research is already looking at brain augmentation with electronics.
So what will be the ultimate limit? Or will humans achieve immortality?
I'm fairly certain that science will get us to a point where we no longer have to die. Even where we can remain young artificially and live a decent life as we age. But this has always been the stuff of sci-fi where it ends up being a curse rather than a blessing. I doubt that we'll conquer other worlds to inhabit before the medical breakthroughs for this are achieved, though ... so that means that all of society would need to change drastically. Then who decides who lives and who can never be born ... that's where it gets scary to me.
The rich and connected ... hell no.
Or will the cosmo or Mother Earth decide they've had enough of us? We live in a very fragile world where any day the sun could belch and destroy life as we know it ... an asteroid could bump the moon out of orbit destroying us in the process ... or a super nova from light years away could bombard us with radiation that would burn the Earth to a crisp. Then there could be new organisms that evolve that would wipe out humanity long before science could combat them.
I like things the way they are ... death is simply the big unknown ... you either enter the next amazing adventure, or all is dark for eternity.