I doubt there is any threat. That line of succession is pretty set unless someone meets an untimely demise. Charles and William are still respected enough even if they might not be quite as popular at the moment.
The Mountbatten-Windsors haven't all exactly been saints. Phillip was quite the ladies man. Had some pretty wild "lunches with the boys" back in the day.
Margaret was a party girl.
Andrew and Fergie haven't exactly had a traditional relationship.
If Harry was or is getting it on the side it's just family tradition. Meghan is smart enough to know and she's apparently pretty well versed on their history. I wouldn't be surprised if she hasn't been a part of it. She's Canadian after all. LOL
Pictures are what got Phillip in hot water. You can rest assured there are no cameras at any Royal "events".