Less than a year after Deborah Norville succeeded Jane Pauley on NBC's "Today" show, network sources are speculating that national correspondent Katie Couric will replace her.

Don Browne, executive vice president of NBC News, denies the rumors, saying it's too soon after Norville's arrival to change the show's co-hosts.Couric, 33, is scheduled to substitute for Norville when she goes on maternity leave in the spring.

"She's no substitute - she's the successor," an unidentified source told TV Guide in its Dec. 29 issue. "Deborah's a bright woman, but she doesn't come across that way on camera. She comes across as plastic. Katie's real."

Couric, 33, joined NBC in 1989 as deputy Pentagon correspondent. She has filled in several times as weekend anchor of "NBC Nightly News" and is scheduled to sub for "Nightly News" anchorman Tom Brokaw on New Year's Eve.