Bill Cosby, who ruled the ratings for nearly a decade with “The Cosby Show,” is returning to weekly series television next fall, according to sources.The vehicle will be “The Cosby Mysteries,” which launched as a telepic Jan. 31. The original game plan was for Cosby to do four movies as New York supersleuth Guy Hanks, and eventually spin out a series. However, sources close to Cosby say he wasn’t crazy about the two-hour format and was anxious to move the show into a regular hourlong drama. An NBC spokeswoman declined comment, but details are being sorted out and an announcement should come later this week, with production likely to begin in May. The show is produced by NBC Prods. in association Columbia Pictures TV, with Cosby, William Link and David Black as exec producers. NBC used its Super Bowl telecast to promote the vidpic, which scored a 14.8 rating, 22 share in Nielsen — a solid rating, though it had to settle for third place in its time period. Cosby led NBC’s first-place assault for eight seasons, from 1984-92, as star and exec producer of “The Cosby Show.” His last series outing was as host of a syndicated gameshow, a revival of the old Groucho Marx vehicle “You Bet Your Life.” The show foundered in the ratings and was canceled before it completed its first season.