In 487, the GPC mentions that Duke Lucius of Caercolun is slain after an ambush by Saxons, who take a part of his land. However, the greater part of the duchy still remains in Cymric hands (at least for now.) So what happens to these lands, and who rules them?

I see a few options, but I wanted to get others' thoughts on this first.

Short term:
1) He has an heir who does what he can to take Caercolun back, ultimately unsuccesful.
2) He has an heir who the Saxons keep as a hostage.
3) He has no heir, or his heir(s) die with him, leaving the rump of the Duchy back in Uther's hands. Would he give it to someone else, one of his favoured vassals? Perhaps 'promoting' either the Earl of Caerwent or Caercolun to the Ducal seat. I could imagine Uther wanting more control in the area for himself, as he seems to have trouble with his Ducal vassals in general (excepting Ulfius, of course.)
4) He has no heir, and the position of Duke falls by the wayside, with the two Earls becoming direct vassals of the King until they are conquered in turn later on.

Long term (Once the Saxons have taken over the rest of the Duchy):
What happens to the Duke and Earls once their land is conquered (providing, of course, that they survive? Do they continue to hold the title in name, or are they lost along with their lands? If it is the latter, I'm certain that their potential heirs would still maintain a claim on the lands and titles, once they are reconquered during Arthur's reign.

Thanks,
-RI.

Our campaign is set in Hertford, with some significant ties to Caercolun. So this was a very pertinent question for me planning for the first session. Without going into gory detail, here's what happened:

485 - Sir Elmig ap Lucius, eldest son of Lucius, is met and takes a liking to one of the knights. There is a promise by that player knight to come to Caercolun and kill Saxons. Another player knights develops a close relationship with one of Earl Hertford's younger daughters; but, she is way beyond his station.
487 - Making good on the promise, our player knights foray into southern Caercolun (now controlled by Saxons) and make a nuisance of themselves. Major Wounds abound. They learn of the death of Lucius.
488 - Elmig is made Duke.
489 - The younger daughter mentioned above is betrothed to Duke Elmig. A tryst with the player knight before the marriage makes the lass pregnant. Trouble ensues.
490 - The child is born, a boy. He's hidden away at Amesbury. During the Battle of Lindsey the player knight (father of the boy and former lover of the Earl's daughter) has a Major Wound and tries to find his way back to camp. Whom should he encounter but Duke Elmig alone, equally wounded. Death and mayhem ensue. Duke Elmig is history and our player knight escapes with no one realizing what he has done.

At this point the player knight (father) hasn't had a chance to play, so its been a bit of a hiatus on this story line. The plot can go many, many ways. It should be interesting. I won't say more because that player reads this board.