I found this on Google:
If it's a boy...
George George has been the consistent frontrunner for the male heir with odds running around 12/1. There have been six King Georges reigning over England including the present Queen's late father who was born Albert but chose to be named King George after his coronation.
James The name has strong royal ties, with two English Kings and six Scottish Kings named James.
Edward Edward is an old English name meaning "wealthy guard" that has been used in the royal family since the 11th century. The name would honour the youngest child of Queen Elizabeth, Prince Edward.
Charles Prince William and Kate may want to pay tribute to Prince William's father, Prince Charles, in the form of a middle name. There have been two Kings of Britain named Charles, with the name deriving from the French word for "Manly".
Harry Another possibility is that Prince William will pay tribute to his brother, Harry, whose name is used as a nickname of Henry and Harold and means "home ruler".
Francis Kate's father's middle name is Francis, and Princess Diana took the female equivalent, so the royal baby may be named after both.
Philip The royal baby's middle name could pay tribute to William's grandfather, Prince Philip, who recently celebrated his 92nd birthday in June.
Michael Prince William and Kate may choose Michael as a middle name, after Kate's father, and reminiscent of the Queen's cousin, Prince Michael of Kent.
Do I need to post the link? Please let me know.