Indeed, this is my concern, too. I am in the midst of writing a memoir (actually several) that I know my family will hate (they've already disowned me) because it tells the truth. And people who have done bad things or have fallen under the influence of someone who has done really bad things, they hate it when others tell truths they have fought so hard to pretend away. While I empathize with the idea that the children have been thrown into a really difficult situation that will very likely damage their future, I've got to say: blame should not be put on the truth tellers.
The very idea of holding out for the possibility that they might be let back in in the future is an anathema to me. That would be like me holding back on that truth telling in public--as I have done for a very long time, only to be slapped hard and kicked as well. Yes, it will negatively affect the children's relationship with grampa, but quite frankly, that relationship seems to already be a hopelessly toxic relationship. At Charles's age...(same age as I BTW)...he's not going to change. He's definitely not going to go thru the therapy that he very definitely needs in order to be a decent grandfather. I did my stint in therapy for more than 30 years. It's really way too late for anyone to start that kind of change now, especially given how grampa thinks so narcissistically of himself alone.
Harry and Mehgan are in an impossibly difficult situation. Damned if they do. Damned if they don't. That's going to be a murky, messy, sucking-to-death quagmire no matter what they do.
What has been made clear by the so-called Royal "Family" is that their royalty has killed their humanity. Not to mention effectively killed Diana. When you have to present a fake persona in order to maintain a fake public institution, it is nothing but multiple disasters waiting to happen. There have already been way too many as it is.