Microsoft has spent three years honing the Surface line from a bulky, awkward 2-in-1 to the sleek, capable machine that turned out to be the Surface Pro 3. Along the way it has validated the existence of the tablet-laptop hybrid as something that people actually want. The next generation of Surface Pro, most likely called the Surface Pro 4, is set to be released later this year and rumours have been spinning about what it will include, how much it will cost and when it will become available.