I have been thinking about this for some time now and I don’t think Disney has to close the Rivers of America, but it will need to be rerouted. In addition, the train will need to be rerouted and the queue for the Hunted Manson will need to rerouted for additional room on the walkway.
I took the time to draw what I was thinking. As you can see from the drawing below, they have enough room for 4 attractions and 4 restaurants in areas. It’s BIG.
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I just can’t wait to see what Disney is actually planning.