Sadly I think that is too much to hope for.
He would have to develop self awareness for that and it seems a little late for a complete change of personality.
Although a tiny bit of me wonders if he has begun to notice and dislike M’s deficits in how she relates to her children.
It would be one thing to excuse her behaviour to staff, his family, friends and even (who knows) to himself but quite another if she is as narcissistic as she appears to be in general towards her children.
It would become more obvious as they reach the sort of ages they are now and can express themselves.
If they fail to do her bidding and provide sufficient worship her anger may well be very unsettling for H to see.
I am not blind to Diana or indeed Charles faults but H had parents who loved him and were kind to him.
Watching M in action as a mother might come as quite a revelation.
Not saying this would be the only reason for the current situation at all, it is clear that finances, H’s loneliness and probably M’s desire to ditch her albatross husband are in play but possibly H is not that unhappy about his wife living elsewhere.