In case of the normal mobile processors, a fan-cooling solution is mandatory. However, if the rumors are true, Microsoft seems to have developed a fan-less design with small vents that allow hot air to flow out of the chassis.
Other speculations suggest a 12inch display with a resolution similar to the Microsoft Surface Pro 3 (2160×1440). Apparently the Surface Pro 4 could be thinner than its predecessor but quite comparable both size and weight-wise. According to Design & Trend, the Surface Pro 4 could feature a bigger 14inch screen with the same 2160p display resolution.
In the meantime, Microsoft has been reducing the price of the Surface Pro 3 for quite a few months now and it seems like the company wishes to a maximize the profits. Recently, Microsoft offered a $150 price cut to the various i7 and i5 variants of the Microsoft Surface Pro 3. The i3 model did not receive a discount and the entry-level Surface Pro 3 model is currently priced at $799.
Most sources seem to indicate that Microsoft could launch this at any time after Windows 10 GA, but product won’t ship until August or September to include Intel’s next gen Skylake processors.