.
Very individual dependent. Bolt set his 100 and 200m WRs just before he turned 23. Linford Christie was 33 when he set his 100m PB. Athletics is littered with massively quick juniors like Lewis-Francis who didn't get any faster as seniors.
LRZ is incredibly quick, but without concentrating on sprint training I doubt he'll get much faster and over time injuries and the inevitable bulking up are likely to take an edge off. May on the other hand looks like he's lost a yard, would be interested to see how he compares to Watson who I always thought has pretty stellar acceleration.