I posted this idea 10 years ago on one of these fourms. I still think it's a good idea.
I've actually given this tons of thought over the past few years. First of all, there are actually six 'scenes' in the carousel. Loading, 1900, 1920, 1940, 2000, Unloading. First things first: combining loading and unloading to one scene. That would free a scene to be applied to a new era.
Keep the patriotic theme and name it The Carousel of Progress: The American Century or The Carousel of Progress: America in the 20th Century. Expand the dialog in the existing scenes so that loading/unloading can have more time to occur. In place of the current 2000 scene add the 1970's. In place of the Unloading scene add New Year's Eve 1999. Therefore your six scenes are.
Loading/Unloading
1900 - Turn of the Century
1920 - Roaring 20's
1940 - The War Years
1970 - Growing Influence/Rise of Personal Technology
1999 - Into Tomorrow
The exterior loading/unloading platforms would need to be redesigned but these changes would make the ride semi-timeless. A presentation of life throughout 20th century America: The American Century.