Of all the shows, Illuminations is the most timeless. There are no IPs, and no movie allusions that would date it. The music is basically from the 1990s, but nothing else sounds like it. It will be a long time before we can say the music is out of date.
Fireworks also never go out of style, and all the other effects can go on for a long time.
The globe itself is subject to updates, making the images clearer, or the whole thing bigger and easier to see. Nevertheless it is a great effect.
Of course the latest tech in these areas is projection, and for that Epcot lagoon is not well suited. There's no true backdrop to project onto, and as a 360 degree show, the projection about have to be far larger than anywhere else. Plus the smoke and fog would obscure it. I could envision potential high resolution projections on some of the buildings, I suppose, like Spaceship Earth, Test Track and Soarin'. But you don't want to start slapping projections on the pavilions to make the whole thing into a cartoon. That would seem to be disrespectful of the culture behind them.
Finally, Illuminations is adaptable. Stuff can be added in, removed, changed and otherwise upgraded. The absolute worst thing they could do is cheapen it or IP it with singing birds, Scandinavian Princesses, genies or anything else.
Overall, ROE is so amazing to me that I would probably take an instant dislike to anything that replaces it. Call me a curmudgeon, but any such replacement would have to be absolutely amazing for me to like it.