Its not far fetched.
When you think about it... we have the means to make it happen right now using stem-cells (aka, regenerative therapies), lab on chip techniques, and nanoparticles coupled with adaptive metamaterials.
The main thing is that there hadn't been much investment (nor priority) in this field up until recently.
AI changes the landscape with automated R&D which cuts the time to develop new things drastically, and as its being used more and more, you can actually develop prototypes or even final working technologies much sooner than before and for lower the cost from the get go (well, at this point energy consumption behind AI is the issue, but measures are being taken to optimize LLM's and other more specialised AI's with more capacity coming in from renewables).
Longevity escape velocity (LEV) already kinda guarantees you can live indefinitely if you keep up the therapies (and it should be available by around 2035).
For every year you are alive you GAIN an extra year... so at first you will effectively STOP the ageing at the age you are by the time you begin the therapy and your bio age will then revert slowly backwards - obviously not all the way down to infancy, but your biological age will probably 'stabilize' around 25 or 30 years old (depending on where you are when you began the treatments).
So, you don't need to wait for nanobots to repair your body all the time (Which might happen much later). LEV is the thing to get to - and obviously, its your choice on whether or not to take it.
I actually think Kurzweil here is more accurate in his predictions because of the rapid pace of improvements in AI from one year to the next - looking at where we were with AI's just 2 years ago, or even 1 year ago.
Google already used it to develop over 300,000 new materials - a task that would take humans ridiculously longer to do.
Apply that to regenerative medicine, and you have yourself something better.
Granted, use of AI in the medical field will also have to improve... given the IT infrastructure in place, and bureaucracy... well IT infrastructure isn't so much of an issue if its better used... bureaucracy is another matter that could slow things down.
Still, new medical treatments are being upheld in medicine as is, so this will eventually become a standard too.
Until then, exercise, eat healthy, and look after yourselves (I mean its a fairly good advice for anyone).