It's inevitable, but not for the reasons you cite. Those attractions are on premium land, have outlived their utility, should be replaced to increase capacity and appeal to the current crowds.
It's not the 1950's anymore. Davy Crockett isn't on TV. Riding a steamboat around a fake island on a track isn't all that thrilling.
Some of these attractions like Tom Sawyer Island, The Liberty Square Riverboat, Carousel of Progress, Hall of Presidents, etc. have had a good run, but attendance is low and it's time to move on.
Disney should take a page from Silver Dollar City or even Tokyo
Disneyland. Announce the attractions are closing in 1 year, have a 1 year "goodbye" event for them and close the book in a respectful way.
50+ years was a good run. These are theme parks, not museums.