Major spoiler: Gisela dies in childbirth early in book 5 (they've been married 10 years by this time), so that will be early in S3. I don't don't expect she'll even make an appearance in S3, but she might. Skade is a crazy Dane who is looking to gain power and tries to use Uhtred to get it. He is drawn to her for a time, but it's really the result of his grief over losing Gisela. In the end, they face each other in battle and I think we all know who wins that one. After Gisela dies, he has many affairs but he marries only one other woman. That would be Eadith in book 9. He is about 34 when Gisela dies and about 58 when he marries Eadith. Of course, Cornwell has said there will be two more books, so who knows what he has in store for Uhtred.