Confirmed today: http://uk.movies.ign.com/articles/122/1223814p1.html
IGN: "James Bond will return ... in two years.
Sony reportedly announced today at CinemaCon that, even though Skyfall doesn't open until November, they are moving forward right away on the tentatively titled Bond 24. The studio has slated the film for a holiday 2014 release, a mere two-year gap between Bond films (there were four years between Quantum of Solace and Skyfall)."
"MI6 points out that Bond 24 is also Craig's first 'optional' film from his original contract, which like recent actors before him, was three films and the first refusal at a fourth."