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.