According to CinemaSpy.com Smallville Season 10 is Confirmed!. The announcement would be made within the next two weeks.

“Fans of The CW series Smallville take note: industry sources inform CinemaSpy that the show has been renewed for a tenth season, and that the official announcement is probable before the end of January — possibly to be made on the Vancouver sets — when Peter Roth, President of Warner Bros. Television will visit the Warner-produced shows Smallville, Supernatural…and Fringe” – CinemaSpy.com

still just a rumor until we hear from the CW..