I only took up cycling when I was 49, and turn 57 later this month. I had no endurance background other than sporadic running for weight control and fitness.
Once I shed 11-12kg I didn’t need and started structured training I got to 3.9w/kg relatively quickly on 10-12 hours per week. I found it quite hard to progress past 4 w/kg for a number of years, but moved up to 4.2 w/kg earlier this year after a solid stretch of HV TR training. My weight did not drop to achieve the latest bump
I have eased back a bit since with some other life issues taking priority, but seem to be able to hold that level still. I probably need to be more cognisant of recovery needs as the years pass than i am, but overall the harder I work, the better i get still, so at this point I don’t consider advancing age a limiter, and I haven’t had to increase my load to maintain current levels.
So with structure and discipline, i would say not too hard to get there and not too hard to maintain for many years to come for you!