I think if Charles dies before George is 18 (which I think is highly likely given those pictures of his swollen red hands) there will quickly be a change to Regency rules to sort this.
Harry may step up or refuse or be generally useless. Or there could be a very messy divorce.
Andrew is next.
So to stop that (and save the monarchy) I'd think they could change the male primogeniture rule to be retrospective to all living royals (as I think they should have done) which would put Anne and her children first.
Autumn Kelly would never have been made to renounce her Catholicism if they didn't think this was a possibility.
Not that I'm a great fan of Peter Phillips, but anyone is better than Andrew.