That is not a bad thought, however, the current Duke of York is only 58 years old and the Windsor's have a knack for longevity. I don't think they will save York for Prince Harry and therefore, I believe he will get his own dukedom.
But . . ., look down one more generation and I think the second son of a future monarch could very well become the next Duke of York, Prince Louis of Cambridge.
It all really depends, given that Andrew could easily live another 30-40 years, we might not even see it used for Louis if he marries before Andrew passes away. But yea, definitely out of question for Harry, so I don't think HMQ would take into account of Harry being created Duke of York once Andrew passes. Too much time and too many uncertainties.