Expected to account for 73.4% of a market that has grown more than 260% since 2010



Click to enlarge.

Gartner Inc. is a lot better at telling you what’s already happened than predicting what’s about to.

Witness Thursday’s report on worldwide tablet sales in which it describes Apple AAPL as having a “free run” in the tablet market this coming holiday season, accounting for nearly three quarters of the 63.6 million units sold before the end of the year.

Android tablets are “on pace” to sell 11 million units for a 17.3% market share, according to Gartner. That’s up from 14.3% in 2010, but a full 28% lower than the number Gartner projected just three months earlier.

Looking four years ahead is even more treacherous. As the chart above shows, Gartner expects Android to have nearly caught up to the iPad by 2015, Microsoft MSFT to be selling nearly 34.5 million tablets per year, and Research in Motion RIMM , using the QNX OS, more than 26 million. Given the collapse of RIM’s PlayBook sales last quarter and Microsoft’s long history of tablet failures, that sounds like some pretty wishful thinking. If Hewlett-Packard HPQ hadn’t pulled the plug, would Gartner have been projecting 2015 sales in the tens of millions for the TouchPad as well?

Gartner’s research VP Carolina Milanesi, for one, seems to be under no illusion about how tough it will be for any competitor to catch up to the iPad.

“Apple delivers a superior and unified user experience across its hardware, software and services,” she says in a prepared statement. “Unless competitors can respond with a similar approach, challenges to Apple’s position will be minimal. Apple had the foresight to create this market and in doing that planned for it as far as component supplies such as memory and screen. This allowed Apple to bring the iPad out at a very competitive price and no compromise in experience among the different models that offer storage and connectivity options.”

Still, Milanesi professes great hope for Google’s GOOG next Android release, “Ice Cream Sandwich,” which is supposed to address the problem of fragmentation among competing Android tablet manufacturers. “Android can count on strong support from key OEMs, has a sizeable developer community, and its smartphones application ecosystem is second only to Apple’s.”

Second only to Apple’s. We’ve heard that before.