iOS will retain a market majority through 2014, then slip under the 50 percent bar the following year, said Gartner analysts Carolina Milanesi and Roberta Cozza, who cited Apple's reinvention of the tablet as key to the company's success.
In 2011, Gartner is forecasting iPad sales of 48 million, compared to 13.9 million tablets running Google's Android, giving Apple's iOS a 68.7 percent share of the tablet market. In 2012, however, Apple's share will slip to 63.5 percent - even though it will sell over 68 million iPads - as sales of Android-based tablets surge to 26 million to account for nearly a quarter of all devices.
By 2014, Apple's share will have dropped to 51.8 percent on sales of 115 million tablets, while Android sales will have climbed to 76 million, representing 34.2 percent of the market.
According to Gartner's forecast, iOS will fall under the 50 percent mark for the first time in early 2015, even as it sells a record 138 million iPads throughout that year.
Apple's dominance would have been threatened even earlier but for Google's decision to not open Android 3.0 - dubbed 'Honeycomb' - to third parties, as it has with earlier versions of the operating system.
Google's change was a reaction to criticism over the Android smartphone market's fragmentation - and that the tablet market would suffer from the same - said Gartner's analysts. But the move will probably mean that prices won't drop as fast as they otherwise would - tablet makers won't be able to decide what's in and what's not in their implementations of Honeycomb - and that Android may find a ceiling on market share.
"The new licensing model Google has introduced with Honeycomb enables Google to drive more control, allowing only optimal tablet implementations that don't compromise quality of experience," said Gartner's Cozza. "This might mean that prices will drop at a slower pace than what we have seen in the smartphone market."
Gartner's take on rivals to iOS and Android was bleak: By 2015, RIM's QNX - the operating system destined for the not-yet-released PlayBook - will have just 10 percent of the tablet market, while others, like HP's WebOS and Nokia's MeeGo, will still be in the single digits.
Even as its market share slips, Apple's iOS and iPad will remain the benchmarks to beat, said the Gartner analysts.
"Many [tablet vendors] are making the same mistake that was made in the first response wave to the iPhone, as they are prioritising hardware features over applications, services and overall user experience," said Milanesi. "Tablets will be much more dependent on the latter than smartphones have been, and the sooner vendors realize that, the better chance they have to compete head-to-head with Apple."
Apple's iOS will dominate the tablet market through 2015 even as rivals catch up.