READ!
http://www.tuaw.com/2012/03/01/retina-display-macs-ipads-and-hidpi-doing-the-math/
Whether it is "Retina" or not is not just decided by PPI alone, but with consideration of the VIEWING DISTANCE!!
This is why the New iPad, which has 264 PPI, is still called "Retina." People see iPad screen from farther distance than from iPhone's so we can call the New iPad "Retina", even if its PPI is below 300.
Same thing goes for Macs. People see Mac screen from even farther than from iPads. In this case, Apple does not need to double the pixel density of MacBook Airs, they just need to add 15~20% more pixels to make Airs "Retina."
for example)
current MBA 11.6-inch = 1366*768
new MBA 11.6-inch = 1600*900 = "RETINA" !!!!
Image
again...
READ!
http://www.tuaw.com/2012/03/01/retina-display-macs-ipads-and-hidpi-doing-the-math/
Reading doesn't harm you!! Your grandfather already told you that, didn't he?