I actually just saw Frozen last week! I loved the music and it was beautiful to look at.. but the plot seemed a little weak somehow. Maybe a sequel could do good things, if they take established characters and launch into an interesting story they could do a lot in 90 minutes.
I think whether Frozen 2: The Return of Jafar is successful depends on whether they can write another "Let it Go". I think the song really carried the film, and it has been played on the radio constantly since the release.