Research company Ovum is predicting tablet purchase to continue exploding over the next four years, but forecasts Apple to lose its market dominance.

Ovum predicts global shipments of portable internet devices based on ‘lite’ operating systems (OSs), which include tablet computers such as the iPad, will hit 150 million per year in 2015. Ovum also reckons 35% of global shipments in 2015 will arrive in the Asia-Pacific region, a huge growth from 2.8 million in 2010 to 52 million in 2015.

The portable devices tracked in Ovum’s forecast are those that use ‘lite’ OSs such as Apple’s iOS, Google’s Android and RIM’s BlackBerry Tablet OS and include tablet devices such as the iPad, Samsung Galaxy Tab and the BlackBerry PlayBook as well as clamshell and convertible form factors.

“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 Ovum principal analyst Tony Cripps. “This will either be as a ‘third device’ where there is a high-penetration PCs or the primary computing device where there is low-penetration.”

A particularly bold prediction was that Apple be cut up by competitors by 2015, with Google’s operating systems, primarily Android but also likely to Chrome OS, to dominate the market.

“We believe that Apple constituted 90% of the market in 2010. However, by 2015 we expect this market share to drop to 35% and Google’s market share to rise to 36%,” Cripps said. Other software platforms, such as RIM’s Blackberry Tablet OS and HP’s webOS, will find some success but between them all they will only account for 29% of the market.