LOS ANGELES -- Katie Couric, Mayim Bialik and Aaron Rodgers are among the future guest hosts who will fill in for the late Alex Trebek on “Jeopardy!”The show announced Wednesday that Couric, the journalist and former “Today” show host, will become the first woman ever to host the show.Trebek, the face of the show for 36 years, died from pancreatic cancer Nov. 8, and the final shows he recorded aired last week.