Would Germany reach the Type XXI before war in Europe?

Could Germany develop and mass-produce something like the Type XXI before a delayed European war?

It might reach a Type XXI-like design through continued iteration, but Allied anti-submarine warfare would also be substantially better by then.

Germany might reach something resembling the Type XXI by 1942 if it continued building and refining successive submarine designs. The absence of immediate mass production would allow more iteration before committing to a wartime standard. That advantage would not be one-sided, because British experience against Japanese submarines would expose weaknesses in ASDIC practice and accelerate new weapons. A later European submarine campaign could therefore begin with more advanced boats facing more mature anti-submarine defenses.