Many congratulations to Meghan and Harry on their engagement.
I will make a prediction here. Everyone seems to think that the couple will be named Duke and Duchess of Sussex on their wedding day. (Well, that HRH Prince Harry will created Duke of Sussex.) I predict not.
I believe that The Queen will repeat what happened with HRH The Prince Edward on his wedding day, when he was created Earl of Wessex with a remainder on the Dukedom of Edinburgh, and will create Prince Harry an earl. As the second son of a prospective sovereign and with HRH The Prince Andrew having two daughters who are restricted from inheriting their father's title, I think that there will be remainder for the title Duke of York, the traditional title for the second son.