I suspect this will be the case, at least for a generation or two - given that the King will most likely have passed away by the time George marries, he won't need a title to hold him over the way William did, so Cambridge will be free to give to Louis. That being said, given the lack of other options with Sussex, Gloucester, and Kent occupied for the foreseeable future, and only Edinburgh and Cambridge to spare of the royal titles (once Prince Edward's life peerage ends, that is), I wonder if there will be any thought given to reviving Clarence, or Windsor, or elevating Inverness to a dukedom again, since, although Andrew holds it as an earldom, it's not as tainted by association with him - even in a stripped down monarchy George's children will likely still be granted titles. But that's quite a ways off, obviously