Nope. When the Smithsonian investigated that rumor, what it found was that Harper Lee had written Capote's work.
And his other dozen novels as well? Methinks the Smithsonian has no reason to take the dissolute Capote's word against Ms. Lee's .(he's dead, she isn't) Clearly, the characters from the book originated with her, but I think thats as far as she got. JMO.