The current Illuminations isn't that great imo, I miss the original version. I think a change is overdue for Epcot's night time show, WoC type show would be a great idea for the lagoon.
I wouldn't be so harsh on my old favorite RoE. With that said, it's dated. Having seen what they can do with the shows like WoC,
Disneyland Forever, and Parc Disneyland's latest spectacular, it needs to be refreshed. 1999 is not cutting edge anymore, and the tools from amazing fountains, powerful pyrotechnics,and awesome projection technologies make it even more of a sore thumb.
The compelling story and theme of Illuminations is thoughtful and inspirational, and fits beautifully into the World Showcase. So thematically perfect. Not to mention that excellent sound track. Sadly it's no longer up to today's standards. It's ready to be retired.
Speaking of doing a WoC style show, there are several issues with that. Remember that WoC projection style is flat, and if you're out of the field of view it suffers dramatically. Whereas Illuminations is completely viewable from any direction. WoC Projection works well in DCA were there's a large accessible path to exit from, but World Showcase is designed for people to linger. The shops, dining, and nightlife are large revenue sources. If everyone had to congregate to one area of World Showcase Lagoon they'd be drawn away from all those establishments. A money loosing proposition. Not to mention all the infrastructure and implementation issues. Also there's no backdrop like California Screamin', Mickey's Fun Wheel, or Everest.
I think RoE's successor will be a fire works show, with barges.