Despite all the rumors, Paul McCartney was always meant to sing Bond theme "Live And Let Die"
Archival contracts show that Paul McCartney wasn't going to be replaced by a female singer, as he previously indicated

While not all James Bond theme songs are created equal, there’s no difficulty in naming Paul McCartney and his band Wings’ rock ballad “Live And Let Die” as one of the best to soundtrack the spy film’s opening credits. The track even earned the franchise’s first of many Academy Award nominations for Best Song.
Granted, the story retold by McCartney and former Beatles producer George Martin throughout the years is that the English singer-songwriter was almost replaced on the track, as producer Harry Saltzman allegedly wanted previous Bond singer Shirley Bassey on the record. However, the fabled rock story seems to have been built on a bit of good old-fashioned miscommunication, as newly unearthed documents show that McCartney was always the first choice for the Roger Moore 007 feature, according to The Guardian.
The detective work comes from Allan Kozinn and Adrian Sinclair, two authors of the recently released The McCartney Legacy: Volume 1: 1969-73, who discovered archived contracts from McCartney’s lawyer (and father-in-law) Lee Eastman and those representing Eon Productions.