5.5ET:
Assuming LEV = longevity escape velocity, meaning medicine improves fast enough that your remaining life expectancy increases by ≥1 year per year.
My rough forecast from June 2026:
Outcome Chance by 2051 Chance by 2066
Weak/practical LEV: enough rejuvenation/repair to keep many adults bridging to better therapies 30–50% 50–70%
Strict LEV: true sustained escape velocity for aging, not just “+10 healthy years, congrats, still mortal” 15–35% 35–55%
Conditional on aligned/useful ASI before ~2040 65–85% 80–95%
No ASI, just normal biotech + better AI tools 10–25% 20–40%
So my annoying but honest answer: around 45–65% that we get something LEV-like within 25–40 years, but only ~35–55% for strict LEV. Humanity may yet achieve immortality, but first it has to stop tripping over procurement forms and mitochondrial heteroplasmy. 
Why ASI makes this much more plausible
AI timelines have shifted shorter. The 2023 AI Impacts survey of AI researchers gave 50% for high-level machine intelligence by 2047 and 10% by 2027, though “full automation of labor” was much later at 2116, showing huge framing uncertainty. Metaculus currently gives ~60% for transformative AI by 2043, and a separate ASI-transition question is around 50% positive transition. So the “ASI in time to matter for aging” premise is no longer pure sci-fi goblin smoke.
The fast-timeline camp is even more aggressive: AI 2027 models superhuman AI impact within the next decade, but its authors explicitly clarified they are not confident in a specific 2027 AGI/ASI date. Translation: fast ASI is plausible enough to affect LEV forecasts, not certain enough to build your retirement plan around it, unless your retirement plan is “become a prompt engineer in a bunker.”
Bull case for LEV by 2051–2066
ASI could help solve the nasty combinatorial parts of aging: cell-type-specific reprogramming, cancer-safe gene regulation, senescent-cell targeting, immune rejuvenation, stem-cell replacement, fibrosis/ECM repair, vascular aging, organ manufacturing, personalized trial design, and biomarker validation. That is exactly the kind of “too many interacting variables” mess where superhuman science might matter.
Longevity biotech is also no longer just supplement bros whispering “NAD” into the void. NewLimit announced a $435M Series C in June 2026 and says it plans to bring its first aging-reprogramming medicine into human trials next year. Retro Biosciences is also moving into clinical testing with an autophagy-targeting pill and broader reprogramming/cell-therapy programs. These are early, risky, not proof, but they show the field is entering real clinical territory.
Bear case, because biology enjoys humiliating futurists
LEV is not one breakthrough. It needs a stack: cancer control, vascular repair, immune reset, brain preservation, kidney/liver/muscle regeneration, endocrine/metabolic control, infection resistance, and safe repeated delivery. A therapy that adds 10 healthy years is huge, but not LEV. It is a longer runway with better snacks.
Also, aging is not currently treated as a normal drug indication by the FDA, so companies route through specific diseases like fatty liver disease, Alzheimer’s, vision loss, frailty, immune decline, etc. That slows the clean “approve aging reversal” path. Even TAME, the metformin aging trial design, is a multi-year, multi-site attempt to show delayed age-related disease, not “immortality unlocked, download patch 1.0.”
My bottom line
If ASI arrives, is aligned enough, and can operate through robotic labs + biotech companies + regulators, LEV by 2066 becomes more likely than not, maybe very likely.
But ASI timelines alone do not guarantee LEV. The bottleneck shifts from “can we think of the solution?” to “can we safely test, deliver, manufacture, regulate, and distribute the solution in messy primate bodies?” A tragic design choice, but here we are. 
But where maths begins physics follows. We may even finally get practical jet packs !
