Pierce Brosnan has now confirmed via a statement on his official website that he will not be returning to do Bond 21.
Brosnan had the following to say...
"I would like to thank all of you who have supported me over the last year or so in regard to my playing Bond. It was a decade of my life that I will always hold dear to my heart and a time that will never be forgotten. And you dear friends stood by me throughout. Many, many thanks! But everything comes to an end, and one must accept this decision which cannot be dealt with in any other way but with some kind of grace and knowledge that I did the job to the best of my ability."