In 1978 many in Germany were still in deep denial over what had happened; Marta and her family seem to represent this legacy of the war. That said, many spouses of prominent Nazis endured the rigours of denazification, including military interrogations to learn whether they might be war criminals themselves; defendants faced imprisonment, confiscation of assets, and blacklisting from employment. Marta might have ended up like Emmy Goering - penniless, widowed, and unable to work.
I can see Martha marrying again, with an old nazi that keeps a lousy job. They'd discuss a lot and she would be passive-agressive with him, telling him that Eric was a better German than him.
I see the children failing at school. The boy will be a workman and the girl will be a shop assistant. One of them will be ashamed about his father's past, maybe the girl, maybe she'll be interested in politics (left-wing, protests, working in a newspaper?) in the sixties and she'll be the opposite of the "ideal German woman" from the nazis. The boy was way older than her during the war, he was a young nazi wearing uniform saying disturbing things about animals, he was brainwashed, so probably he'll have problems (angry issues, alcohol) but he'll maintain a strong bond with her sister anyway. I think the girl will try to get back in touch with her uncle too.
Marta had health problems at the beginning, and her last scene showed her looking off in health. The death of her husband & the loss of their privileged lifestyle would be too hard for her to survive long after. I often imagine the son getting bullied by Jewish peers wanting to settle scores.