MMA Weekly has an interview with Randy confirming the rumors:
In a meeting with Ultimate Fighting Championship president Dana White last Tuesday, current heavyweight champion Randy Couture turned down a proposed title defense against Antonio Rodrigo Nogueira at UFC 81 on Feb. 2, 2008. There was also some fence mending to be done at the meeting. Following Couture's resignation from the UFC in October, the two went a couple of rounds through the media, disputing the basis of the resignation. With the meeting, Couture said he was able to air out the issues addressed in his decision and looks forward to a cooperative relationship with his employer of eleven years.
It looks like Nogueira/Sylvia will be for the title in February. This news is nothing short of devastating for the UFC, no matter how it is spun. The piece also suggests Couture won't be going anywhere to fight Fedor. This may be why Dana said on a recent radio show that he hopes he can still book Fedor and Randy to fight one day, as that looks like the only way to get Randy out of retirement at this point. Of course, it wouldn't shock me if in a year Randy feels the same desire to get back in there he felt before.