ARM confirmed that the first 20nm processors should appear in late 2013. The new chips should deliver superior performance and power efficiency compared to existing designs. Of course, there is still no word on what to expect in terms of specs, but it is more or less obvious that we are looking at dual or quad-core A15 parts with next generation graphics.
However, the transition to 28nm does not appear to be going smoothly. ARM heavyweight Qualcomm was the first to introduce a 28nm design, the stunning Snapdragon S4 based on its Krait core. But the outfit is now struggling to meet demand for S4 chips and it is basically becoming a victim of its own success. Other ARM players, such as TI, Nvidia, Samsung and Apple, have yet to introduce a single 28nm part.
With all this in mind, a transition to 20nm in 15+ months sounds rather optimistic. It is not impossible and we would like to see ARM pull it off, but it is clear that A15 chips in 28nm will dominate the market in 2013, while volume shipments of products based on 20nm chips are probably coming in 2014.