Disney executive Jennifer Lee addresses the surprise announcement regarding Frozen 3 and Frozen 4. Following the big success of the first film in 2013, a sequel continuing the story of sisters Anna (Kristen Bell) and Elsa (Idina Menzel) was released in 2019, eventually becoming the highest-grossing animated movie of all time. It's no surprise then that Frozen 3 was confirmed in February of this year, but Disney CEO Bob Iger recently announced that Frozen 4 is in the works as well.
https://screenrant.com/frozen-3-4-production-disney-explained/