They've canned projects that were likely much farther along than whatever this project is/was. Most famously perhaps, The Western River Expedition was so far along that they apparently already had a number of animatronics built for it (I believe some of which are now used in Living with the Land), I think land was even being prepped for the ride as well. From what I hear, WRE was pretty much ready to be physically built (and parts already were built), but it was replaced by an abbreviated version of POTC after WDW goers complained of its absence upon Magic Kingdom's opening.
There have been plenty of other announced (and likely well into development) projects that never made it, some late in development and on the verge of being built. Westcot is a good example of an entire park. There's also all the rides cut out of the budget for Animal Kingdom (Tiger River, The Excavator Beastly Kingdom). Fire Mountain and Bald Mountain for Magic Kingdom, no doubt among numerous others. There were also plenty of announced (or ones we've seen models of) World Showcase pavilions or expansions that never made it- Matterhorn for a Switzerland area, Mt Fuji for Japan (and another version with a planned dark ride apparently), Rhine River Cruise for Germany and many more pavilions and/or rides mentioned over the many years of the park. Hollywood Studios had Dick Tracy (first name being short for Richard if the forum censors it) and Muppet rides planned, among other things i'm sure.