Queen Elizabeth's successor

[MASHED POTATOES. VOTE!]

The Prince Charles, Prince of Wales will be her and Prince Philip's successor.

When Philip dies, Charles will be Duke of Edinburgh

Actually from what I've read the dukedom is being intended for the Queen's youngest son, the Earl of Wessex (yes, unlike his bros he's a mere Earl. Sad!) A reigning monarch doesn't hold any peerages by custom and convention, so Charles can't succeed Philip as the Duke of Edinburgh, and Andrew is already the Duke of York.

[MASHED POTATOES. VOTE!]

Also, unless he predecease his mother, there is no way on earth Charles passes on the crown, even if he's well over 70 when the times come. Given his parents' longevity, it's possible for him to become the oldest successor and still have relatively long reign.

Gustaf VI Adolf of Sweden didn't become King until he was already 67, and yet ruled for 23 years (1950-1973).

[MASHED POTATOES. VOTE!]

The Prince Charles, Prince of Wales will be her and Prince Philip's successor.

When Philip dies, Charles will be Duke of Edinburgh

Actually from what I've read the dukedom is being intended for the Queen's youngest son, the Earl of Wessex (yes, unlike his bros he's a mere Earl. Sad!) A reigning monarch doesn't hold any peerages by custom and convention, so Charles can't succeed Philip as the Duke of Edinburgh, and Andrew is already the Duke of York.

So does Harry become Duke of York in addition to Sussex when Andrew dies?

According to the wiki, the Dukedom can be inherited only by "heirs male of the body lawfully begotten", and Andrew only has two daughters. So the title will become extinct until it's likely revived.