There were plans to get Sean Connery back on two separate occasions, for the 40th and 50th anniversary movies. Die Another Day was going to have a casino scene where Bond encountered his father, played by Connery, at one of the tables. Director Lee Tamahori, originator of the idiotic 'Bond is a codename' theory that has stunk up the place ever since, thought it would be cool - note that this is the same guy who thought a CGI bullet in the gunbarrel sequence and the infamous CGI windsurfing sequence were also cool. Fortunately, nobody else did and the idea was nixed. In Skyfall, an early draft of the script had the eponymous home being a retirement house for 00 Agents and a former agent played by Connery would have helped Bond fight off Silva. That idea was ditched and Connery was considered to instead play the role of Kincade, the Skyfall housekeeper, in the final draft (which pretty much everyone assumed because Albert Finney looked a fair bit like Connery in the part and had lines like "Welcome to Scotland"), but Sam Mendes - who confirmed the rumour - said it was ruled out because he thought it would break the audience's immersion in the film.
Another interesting Bond film cameo that never was: Grace Jones, Mayday in 1985's A View To A Kill, was set to pop up in No Time To Die until the very last minute, but she quit because she wanted a bigger part (possibly as big as the black dildo she took into her sex scene with Roger Moore to annoy him). She was set to play the owner of the bar in Jamaica where Bond and Felix go to talk, and would have, ahem, 'distracted' Logan Ash (Billy Magnussen) while he tried to listen in. The bar was inevitably going to be called Mayday's despite the Craig timeline being separate to the other Bonds', meaning Craig's Bond never met the original Mayday. That said, such inconsistency didn't stop them including a portrait of Robert Brown's M in the film, or Bond having his Aston V8 from The Living Daylights.