First Katie Couric, now Meredith Vieira—it is not the best week for network news hosts. Sources say NBC is prepping successors for Vieira, as they expect she will not renew her contract when it expires in September. According to sources, Vieira, 57, is walking away from her $11 million contract because she is tired of the grueling lifestyle and would like to spend more time with her husband, who is ill. NBC is said to be eyeing Today’s Ann Curry and Natalie Morales, as well as Washington correspondent Savannah Guthrie and CNBC’s Erin Burnett to take over should Vieira decide to leave. While Today is the dominant voice on morning television and hugely profitable for NBC, Vieira’s departure could make the show vulnerable.