"Frozen" is Disney's biggest and most successful animation to date, but that does not mean that a sequel could mean an equivalent success, which is why it's not top priority, as far as the studio is concerned.
Disney has decided that the sequel will be a short film instead of a full-length animation, much like what they did with their other hit films. The website, Hallels reported that Disney's CEO Bob Iger said in an interview, "In order to make the perfect movie sequel, the filmmakers have to write the perfect follow-up story for it. Otherwise, Frozen won't be as good anymore and that would surely disappoint everyone."
That does not mean that the studio is not maximizing the franchise potential of the film, though. It will be the next Disney production on Broadway, with four novels set to be written and released soon. Two of the four novels already have titles: "Anna and Elsa: All Hail the Queen," and "Anna and Elsa: Memory and Magic."
Iger noted that the company knows they managed to find a golden goose with the film, but that does not mean that they can easily make another one, and it will take time to make it perfect. For the mean time, Air Herald noted that Disney is going all out on franchise and merchandise, including the launch of Frozen-related media products that included the novels, the Broadway show, and ABC's popular series, "Once Upon a Time," which involved a lot of Disney characters that included "Frozen" characters this season.
According to Variety, the plot of the short, called "Frozen Fever," goes on this way: "It's Anna's birthday and Elsa and Kristoff are determined to give her the best celebration ever, but Elsa's icy powers may put more than just the party at risk."
The magazine also noted that that Olaf will also be making an appearance in the short, which will be directed by Jennifer Lee and Chris Buck, will be produced by Peter Del Vecho. It is also said to include a new original song by writers of the phenomenal song, "Let It Go," Robert Lopez and wife Kristen Anderson-Lopez.
As for the cast, there is no news yet whether or not Kristen Bell and Idina Menzel will be returning, considering that both are busy with other aspects in their lives. Bell is currently pregnant with her second child, while Menzel is busy recording her Holiday Album.