The Strategies for Engineered Negligible Senscence (SENS), put forward by biomedical gerontologist Aubrey de Grey, form a high-level scientific plan of attack, focused on the root causes of age-related degeneration. In essence, it is a declaration that scientists know enough and science is capable enough to move rapidly towards a cure for aging - and all age-related disease. I have this to say in the Longevity Meme introduction to SENS:
Progress in any one area of SENS science is likely to lead to therapies for a class of age-related diseases. It is not unreasonable to expect the research community - motivated as it is to seek cures for specific diseases - to slowly fill in the gaps in SENS as time moves on.
Making gains in SENS science in unrelated bits and pieces is likely to be a slow path for progress towards meaningful healthy life extension, however. Curing any one age-related condition is a wonderful thing for sufferers, but it will not increase healthy life span for anyone else - nor will it lead directly to therapies that can extend healthy life span without further investment and work. It would be much more cost-effective to directly address the root cause of aging and age-related disease.
Incidental rejuvenation of age-related cellular damage may just happen at some point as a matter of course, engineered in bits and pieces by a hundred different scientists working on a hundred different problems. As I point out above, however, don't expect "at some point" to arrive soon enough to be of any help to you personally.
Aubrey de Grey's proposed timeline for the direct, cut-to-the-chase approach can be found at the SENS website:
the first major SENS [milestone, reversal of aging, will] be achieved with laboratory mice. I also consider that it will be the point at which society becomes convinced that curing aging is very urgent, and that it will kick-start a genuine "War on Aging".
My estimate for the time until this milestone is reached, if there is adequate funding [of the order of $100 million / year], is ten years from now; almost certainly not as soon as seven years, but very likely to be less than 20 years. If funding is sluggish this could be doubled.
the second major SENS milestone [can] reasonably be defined as the arrival of therapies that confer a postponement and repair of human aging proportional to that described for mice in milestone 1, i.e. a tripling of our remaining life expectancy with therapies initiated on our late fifties or so. Inevitably I call this "Robust Human Rejuvenation" or RHR.
My estimate for the time until this milestone is reached, starting from the time that the mouse target is achieved, is 15 years; almost certainly not as soon as five years, and could be as much as 100 years. Note that this time I make no caveats about funding, because I think it is inconceivable that shortage of funds will be allowed to slow down this work once milestone 1 is achieved.
A number of us feel that the lower end of this range of timelines is impractical for simple business and commercialization reasons - it takes a decade to get anything out of a laboratory and to patients these days, and that looks to be getting worse before it gets better. Equally, the far upper end starts to look a little silly if you give any credence to Kurzweilian or similar views of the decades ahead - the technology curve four decades from now is going to be very impressive indeed.
The possession of impressive and advanced medical technology does not guarantee that we'll do all that we can with it, however. The laundry list of goals that could have been accomplished over the past 50 years - but were not - is a very long one. Supporting and advocating directed research that explicitly aims to greatly extend our healthy life spans is not a matter of hastening an outcome that was inevitable - it is a matter of ensuring that it happens at all.
100,000 lives are lost to the end results of aging with each and every day of delay, and hundreds of millions more suffer from age-related disease. We can do better than incidental healthy life extension - we can get out there and make it happen within our lifetimes.