I hear this a lot - but I am not sure why so many people think this to be the case. Do you think they blew it with HEA? I myself loved Wishes, but I think HEA is great in a different way and I love the incorporation of the projections. It doesn't get me quite as emotional as Wishes did, but it still gets me when Tink flies.
Personally, I never liked Illuminations as much as Wishes. It's a good show, don't get me wrong, but I find the story being told by the globe to be too far away and unclear to really grasp what it's supposed to be saying. It's been around for nearly 20 years, and so I'm perfectly fine with it moving on. i think modern technologies can use the space much more effectively.
I do NOT think we will get something like World of Color. WoC needs a very shallow lake for mounting all the fountains, and I do not think WSL provides that. I expect a similar show in that it will likely come from barges and incorporate the countries around the Lagoon. It will probably be something that can be presented more visually from the Riviera tower as well.