Microsoft shipped 2.5 million Surface-series tablets in the fourth quarter of 2015, leading to total shipments for the year reaching six million units, or 50% higher than market expectations of four million, according to Taiwan-based supply chain makers.

While global notebook shipments are expected to remain weak in 2016 although the rate of decline is expected to narrow, shipments of Surface 2-in-1 products are likely to grow another 30% on year to eight million units in 2016, the sources estimated.

Microsoft announced recently that its Surface revenues grew 29% on year in the second quarter of its fiscal 2016, which ended December 31, 2015. Increased shipments of Surface Pro 4 and Surface Book contributed to growing Surface revenues, the sources commented.

Additionally, Microsoft has begun developing new Surface models in cooperation with supply chain makers, with new products likely to be unveiled in the second half of 2016, said the sources.

Brisk sales of Surface products have encouraged other vendors, including HP, Dell and Lenovo, to follow suit, indicated the sources.

For example, HP announced its HP Elite x2 at CES 2016. The 2-in-1 model features a 12-inch Gorilla Glass 4 display and an Intel Core M vPro processor, targeting the high-end segment.