I wouldn't say zero chance. Even if for sake of argument we take it as true, both the statement "There is zero chance of seeing a dramatic breakthrough in life

I wouldn't say zero chance. Even if for sake of argument we take it as true, both the statement "There is zero chance of seeing a dramatic breakthrough in life extension within our lifetimes." and "People alive today may live to be biologically immortal." can be true at the same time. Every minor advance medical technology that effectively increases lifespan gives those living more time on the clock to hit one of those major breakthroughs. If we had a sudden breakthrough that allowed us to reverse some aspects of aging resulting in a lifespan increase of 20 or perhaps even 10 years, I would think that those additional years plus the new public attention would give enough time to find further improvements. Eventually you reach the point that the average human lifespan starts increasing per year by more than one year. At this point even if you don't yet know how to make people biologically immortal you're going to drastically decrease the chance of death to the point that many of those alive will live to be biologically immortal. To a lesser degree this applies to all sorts of medical advancements that increase lifespan. All sorts of things could combine to allow those currently living to survive long enough to make use of true longevity treatments. Cures for cancer, alzheimer, and other such symptoms of aging brings us closer to this possibility. At this point it's a lottery game and I wouldn't bet against at least some people winning the jackpot.