Ending months of speculation, Katie Couric marked her 15th anniversary on Today by announcing on Wednesday morning that she is leaving NBC's morning news program. "After listening to my heart and my gut, I've decided I'll be leaving at the end of May," she said on air. The longest-serving anchor in Today history, Couric is expected to fill the anchor chair at CBS Evening News, in a deal the Wall Street Journal says will also get her face time on 60 Minutes, as well as her own documentary crew, and fetch her a cool $15 million a year. "Sometimes change is a good thing," Couric told viewers. "Although it may be terrifying to get out of your comfort zone, it's very exciting to start a new chapter in your life." As for her Today successor, a source at The View tells the New York Daily News that it's all but a done deal that Meredith Vieira will fill the vacancy.