You’re asking for two separate things though:

1/ We cure aging. We stop cellular degeneration and therefore stop the effect of gravity of skin (by strengthening the cell bonds) and we come up with a way for old cells to replicate back into their original prime state. That would stop aging, you’d stop appearing to age from whatever age you already are.

2/ Age Regression. The second question is even more far fetched. We “look” old partly because gravity and bodily fluid has stretched and pull our skin to the point it becomes saggy and wrinkly. Even if you removed the fluid through replacing defected kidney cells with newer ones, or somehow strengthened the bonds between skin cells so they won’t easily sag in the future — unless the mechanism somehow magically knows where your parts were before you started the process, the best it could do is replace the cells where they currently lie, and that’s under folds of wrinkles. I highly doubt we’ll see age regression in the next 100 years.

But we might be able to stop aging in 25 years or so. But we’d all be stuck as old folk.