Ah, I'm pleased for Edward and Sophie - the Queen and Prince Philip had already made it known that it was their wish, and Edward has already done a lot for the DoE award. I know 59 isn't a special birthday, but makes sense to announce it today, as the first birthday since the Queen's passing, and before the coronation.
James is now officially the Earl of Wessex; as pp have mentioned, he is now allowed to use his father's subsidiary title, as a courtesy, as he is the eldest son -I know it's Wikipedia, but this does explain it: https://en.wikipedia.org/wiki/Courtesy_titles_in_the_United_Kingdom
Have new LPs been issued to make the title non-hereditary? (Does anyone know how this works? Has it been done before?)
To be honest, it makes sense - it means that whoever decides to take over the DoE award in the future (probably a working royal) can then hold the title. Personally, I think that would be far too much pressure to put on James at his young age - the likelihood is that he won't be a working royal in the future (as his cousins, the York sisters, aren't), and he doesn't;t want his future role (as Chairman of the DoE award) already laid out for him as a teenager.