Stripping out the impact of exchange-rate movements (constant U.S. dollars), the global computing devices spending will decrease 3.1 percent in 2015. The global PC market is on pace to total 306 million units in 2015, a 2.4 percent decrease over 2014.

"The fall in PC purchases is primarily due to expected price increases by vendors in Europe and other regions, which is forced by local currency depreciation against the dollar," said Ranjit Atwal, research director at Gartner.

"The currency squeeze is forcing PC vendors to increase their prices in order to remain profitable and, as result, it is suppressing purchases. We expect businesses will delay purchases of new PCs, and consumers will delay or 'de-feature' their purchases. However, this reduction in purchasing is not a downturn, it is a reshaping of the market driven by currency."

The mobile phone market, the largest and most profitable segment of the global device market, is expected to total 1.9 billion units and grow 3.5 percent in 2015. The presence of cheaper smartphones will continue to appeal to consumers, and counter the need to increase prices. Mobile phone pricing has been increasing over the last few years driven by a rising premium-phone average selling price, but now will remain flat or slightly down as the smartphone market reaches saturation over the next few years.

"Consumers will continue to prioritize spending on phones over PCs and tablets in 2015," said Roberta Cozza, research director at Gartner.

Worldwide ultramobile shipments, which include tablets and clamshells, are on pace to total 237 million units in 2015, a 4.3 percent increase over 2014.

"Following rapid growth, the current mature consumer installed base for tablets is comparable to that of notebooks," said Ms. Cozza. "Not only is the tablet segment nearing saturation in mature markets, but the influx of hybrids and phablets will compete directly with tablets in emerging markets."

Gartner analysts expect that an increasing percentage of users of high-end Android devices will move to iOS. "Android vendors at the high end are finding it hard to differentiate and add value beyond technology and features," said Ms. Cozza. "Furthermore, Apple's brand clout and ecosystem — alongside the new large-screen iPhone models — are strong alternatives."

"We also estimate that, despite Apple's premium price tags, the iOS base replacement cycle that started in the fourth quarter of 2014 with the larger iPhones will carry on into 2015," said Ms. Cozza.