I don't think Haakon and Mette-Marit will divorce. The reason being MM's health. Let's say they do divorce, MM's health becomes much more dire and the worst happens before she can receive a lung transplant. The optics would look bad, and I won't predict the outcome, but the public could turn against Haakon.
I think MM stepping back from royal duties, engagements and her charities (those that don't drop her) will occur with the explanation that her health can no longer keep up with those activities, which would be true. Ingrid Alexandra may have to finish her Uni studies back home in Norway and become "First Lady" as Princess Astrid did with her father King Olav. I'm just throwing that out.
I've always been a MM fan, but at this moment, I'm angry and disgusted with her. She was carrying on the flirty communications with Epstein and using romantic descriptions, for crying out loud, she's married and had young children at the time. At least, Fergie "was" divorced, living with Andrew, but divorced. I believed MM was smarter than Fergie, but apparently not. I'm angry at the way she's handled the Marius situation/crimes. She should have been a model for parents and demonstrated that she loved her son, but he committed horrible crimes and has to face justice. She abetted with Marius instead.