I have yet to become a Duke after 2.5 years of playing this game but I'm sure there are plenty of others who have been playing longer and haven't had the chance yet, either.
It took me almost exactly two years to get my first duchy. They are hard to come by, no doubt. But that's also why they are so highly valued. Any old noble can eventually get elected as a ruler
somewhere. But you've got to actual
be someone to get a duchy.
Or really lucky.
Anyways, I'm guessing that the Gaston-succession will wait until the war is over before hoping to expand to Darfix?
You'll have to wait and see.