Apple CEO Tim Cook’s assessment that the world is moving into a “post-PC” era during the debut of the New iPad may have seemed presumptuous at the time, maybe even overly ambitious of what Apple’s tablets, along with other manufacturers, but a new Yankee Group report shows that the post-PC world might be on the horizon after all.

The study, “2012 US Tablet Landscape: An All-Too-Familiar Story,” predicts that the number of tablets in the United States will rise from 25 million in 2011 to more than 134 million by the year 2015, overtaking the number of PCs in the country. Nearly 1 in 4 U.S. consumers plan to pick up a tablet by the end of the year, but a quarter of those consumers are still up in the air as to which tablet they’ll eventually settle on. Given that Apple’s iPad family represents 51% of all tablets currently owned in the United States, it is hardly surprising that of those planning to buy a tablet in the next six months, 47% have their eyes on an iPad.

While Apple and its iPad might be gobbling up the lion’s share of the tablet market, that voracious appetite is leaving its competitors to fight amongst themselves for the leftovers. “For the second quarter in a row, Apple’s iPad is leading the tablet market, forcing all other competitors to battle for the remaining 49 percent share,” said Carl Howe, research VP and head of the devices practice at Yankee Group, in a statement. “It’s too late to change current ownership, but tablet makers looking to gain on Apple need to start improving their brand visibility and targeting people who don’t already have their minds set on an iPad.”

To date, the non-Apple tablet makers don’t appear to gaining any ground on the iPad and, worse, could be losing traction. While Amazon’s Kindle Fire was making waves in 2011, that fever seems to have broken: only 6% of prospective tablet buyers intend to buy one, down from 11% last year. Similarly, consumer interest in Samsung tablets has also dropped as only 4% intended to purchase one, down from 7% last year. Less visible tablet manufacturers like Blackberry, Motorola, and Dell face an even grimmer six months ahead, with only 4% of consumers saying that they own a tablet made by one of those companies.

The iPad isn’t crushing its competitors on a wave of sheer hype, either. A recent study from ChangeWave Research found that owners of various iPads are by far and away much more satisfied with their purchase as opposed to consumers who opted for a tablet other than an iPad.

While several of the iPads competitors might perform exceptionally well, Apple has certainly achieved a massive coup in the tablet market by successfully branding itself as not just a tablet manufacturer, but The Tablet Manufacturer.