I disagree completely. Cartoons age way less than regular films do. It's possible that in a few years, the consumer demand will weaken, but in another 10-20 years, when the kids of today have grown, the nostalgia factor will be strong.
You also forget that a sequel is on the way...
Also, I thought Frozen was a great film. They just milked it to death. Once they stop milking it, the film still holds up. Good Music, characters, and story.