Maybe it is theoretically possible to create that army of nanobots, drugs, ... to live a couple of years more. Say, until we all live to be 100 years, at average. But I just think the costs are going to be sky high. Already, you can see that a large part of the cost of health care is providing drugs and treatments for the elderly. It is not uncommon for somebody who's 80 years old and still in reasonably good shape to be using a coctail of 10 different drugs, each day, easily costing two hundred dollars per week, or more.

And, maybe you're thinking "ah, well, the price of drugs will go down as technology advances", and you would be right of course. Generic drugs for common diseases will become cheaper. But as people grow older, they will develop more and more rare diseases and disorders, and some may even be unique. Developing a new drug today takes years, and costs millions, sometimes billions. What do you think is going to happen when you're 98 years old, and develop a completely unique disease that will take 1 year to develop a drug for, and that's going to cost $10 million ? (which is really quick and cheap considering today's standards). People will say "I'm sorry," and will hold your hand until you mutter your last words.