Depending on which powermeters I believe in*, I’m either 4.78 (PM on bike 1), or 4.92 (PMs on bike 2 and 3). I’m going to be 53 in a few weeks.
I’ve been riding since I was 14, but I think that within 5 years, you could get to 4 w/kg. You need the intensity that TR programs provide, but to reach your genetic potential you also need as much low intensity volume as you can adapt from, or that fits in your time availability.
If after a couple of years, you can move from MV to HV plans, that’s the ticket – along with consistency, consistency, consistency in training.
*(higher is always truer! except when it isn’t!)