Anna and Elsa are moving into Princess Fairytale Hall beginning on April 20th. According to the official announcement on the Disney Parks Blog:
Elsa and Anna will appear together each day until the early evening, after which other visiting Disney Princesses will be available to greet guests. Cinderella and Rapunzel will also continue making appearances at Princess Fairytale Hall.
Anna and Elsa are also expected to no longer meet guests in Epcot's Norway Pavilion after April 19th.
April 20, 2014: Anna and Elsa made their debut at Princess Fairytale Hall today. Wait times exceeded three hours for most of the day.
March 14, 2014: The Disney Parks Blog confirmed that Anna and Elsa are moving to Princess Fairytale Hall on April 20th.
March 12, 2014: KennyThePirate.com reported that Disney's entertainment schedule has been updated as of April 20th to include Anna and Elsa and a visiting princess. They have also been removed from the My Disney Experience mobile app as of April 19th at Epcot.