Microsoft is expected to have a chance to ship over four million Surface tablets in 2015, up from two million units in 2014, because of its new Surface 3 and Surface Pro series products, according to sources from the upstream supply chain.

Microsoft is reportedly planning to unveil its next-generation Surface Pro 4 tablet during the upcoming Build developer conference in April. The new Surface Pro tablet is estimated to enter mass production in June and will be released along with Windows 10 in the second half of 2015, the sources said.

Microsoft's Surface 3 tablet, announced at the end of March, is expected to be available in May, priced at US$499 and will be competitive in the market, the sources noted.

Microsoft previously noted that it had shipped 12 million Surface tablets since the birth of the product line and its sales during the fourth quarter of 2014 rose about 24% from the same quarter a year ago.

With the Surface devices, the sources expect Windows-based tablet shipments to exceed 15 million units in 2015, up 30% on year; however, some market watchers are concerned that the Surface could reduce vendors' willingness to launch Windows-based tablets.