Just because Anna Wintour wants something doesn't mean it will happen — surprising but true. Though she is very effective at making things happen, especially when it comes to things that will benefit American Vogue, she is not likely to get Kate Middleton to pose for a cover any time soon. The palace has said Kate Middleton is leading a quiet life out of the spotlight until next year, deciding which charitable causes she will promote and learning about the monarchy and British government. They're only letting her attend public events once a month until then, which is terrible for everyone with an online look book to update. (Also: everyone with eyes and the attention span of a gnat, so, pretty much everyone.) Wintour was rumored to have been pressing Mario Testino, the preferred photographer of the royal family, to encourage Kate to do a cover for American Vogue. The palace has issued a statement to People, saying "There are no plans for the Duchess to do anything with U.S. Vogue."
And it shouldn't be expected for some time. Though Princess Diana appeared on the cover of British Vogue's August 1981 issue before her wedding, which she doesn't seem to have posed for specifically, she didn't pose for a cover of the magazine until 1991. She didn't pose for the cover of American Vogue until 1993 — after she had separated from Prince Charles. So she was a princess for twelve years before she lent her beauty and star power to American Vogue. The monarchy probably isn't keen on looking frivolous by having Kate rush onto the cover of a fashion magazine, and when she does, it will surely be to promote her charitable causes well in the future, rather than just herself and her clothes. And she'll probably go to British Vogue first, because the whole point of her job is to make Britain look good and do her people proud.