^^^ Yes.
Quote:
"When the monarch has no male children, the rights and responsibilities of the duchy revert to the Crown and there is no duke"
Source:
https://en.wikipedia.org/wiki/Duchy_of_Cornwall
Note however:
"Since the passing into law of the Sovereign Grant Act 2011, revenues of the Duchy of Cornwall will pass to the heir to the throne, regardless of whether that heir is the Duke of Cornwall. In the event that the heir is a minor, 10% of the revenues will pass to the heir, with the balance passing to the Crown"
[ibid]