This might be an unpopular opinion, but kids today don't know who Tom Sawyer is, nor do they care about a steam-powered riverboat. Besides, maintaining an island with a steam-powered riverboat circling it every 20 minutes or so gets expensive in the long run, and the infrastructure they had to maintain to keep this obsolete (by today's standards) bit of fantasy going just isn't justified by today's MBA standards.
And the kids of today are the ticket buyers of tomorrow. Better to put something in that THEY can relate to. Boomer G'paw gonna be gone soon anyway...
Think upon this... now that there's another Car ride coming into MK, expect pressure to mount on repurposing the land eaten up by Tomorrowland Speedway...