Katie Couric's departure from NBC and her ascension as anchor of the CBS Evening News will come in two separate stages, published reports said today (Tuesday). She is expected to announce, possibly as early as this week, that she will be leaving NBC's Today show but remain as co-host of the early-morning program until May 31, when her contract expires. The announcement of her deal with CBS will come later, the reports indicated, when final details of the contract are worked out. Today's Washington Post, citing well-placed sources, reported that Couric's job on Today has been offered to Meredith Vieira, co-host of ABC's The View and host of the syndicated Who Wants to Be a Millionaire. The newspaper said that Vieira is seriously considering the offer. Still other reports indicated that NBC's Campbell Brown has the inside track on the Today job.