The iPad accounted for 90 per cent of the 14 million tablets and non-smartphone mobile internet devices running "lite" operating systems sold last year.
By 2015, however, when 150 million sales are expected, the proportion of tablets based on Apple software will have plummeted to 35 percent, the analysts Ovum said.
"This huge growth in shipments will be dominated by tablet-style technologies such as the iPad and will mainly be driven by consumers buying devices to complement their smartphones," said Tony Cripps, principal analyst.
The main beneficiary will be Google, and by 2015 its share of tablet sales will have risen to 36 percent, Ovum said, edging ahead of Apple, currently the world's most valuable technology firm.
The remaining 29 per cent of the "lite" operating system market will be divided between Microsoft, BlackBerry maker RIM, and HP's WebOS, the analysts said.
"The dominant software platforms, Apple and Google, will attract the most attention form the cream of the developers," said Mr Cripps.
"As a result they will have the best, most talked about applications and content and, when all is said and done, this is what people will consider when making a purchasing decision."
Although they are expected to be vying for market leadership, Apple and Google have adopted radically different strategies in the intensifying battle over mobile devices.
Apple has taken a dominant early position by tightly controlling hardware, software and retail. In contrast, Google gives away its Android operating system to device manufacturers, and allows outside software developers more free rein.
But the intensifying battle between the pair is reminiscient of the desktop war between Apple's Macintoshes and IBM-compatible PCs in the 1980s. After taking an early lead, Apple's machines were surpassed by cheaper PCs running Microsoft Windows, which grew a wider range of software as developers revelled in the control they were allowed.
Many industry analysts expect history to repeat itself in the growing market for mobile internet devices.