When the Blackburn Roc might have been replaced

If the Fleet Air Arm had more time, when might it have replaced the Blackburn Roc?

Probably by 1942, but not by 1939 because the Roc had only just entered service.

Replacement of the Blackburn Roc by 1942 was plausible if the Fleet Air Arm had received more development time. A replacement by 1939 was too early because the Roc had only just entered service. Recognizing a weak design did not make a successor immediately available. The answer places aircraft improvement inside the practical lag between requirements, development, and fielding.