[bitL]

This argument won't stand. New phone displays have significantly lower battery consumption than the old ones and substantially higher resolutions. And you can always employ tricks like reducing refresh rate to lower the consumption even more.

[anextio]

New phones are also not tied to the x86 platform, and generally run software that has been optimized from the start for performance.

There are other considerations too. Phone usage patterns are way different to computer usage patterns. The vast majority of phone usage occurs in small blips of activity during which execution can be optimized for the CPU to race to sleep state as soon as possible. Computers don't have the same usage patterns at all, and have a legacy of first and third party software (on all major platforms) that have not yet been optimized for performance.

[rayiner]

There isn't a retina notebook yet with the kind of battery life the Air has.

[TazeTSchnitzel]

Why not? If they push the resolution of the 11" much more, it'll become harder to read the screen. If they double the resolution to make it "retina", the battery will take a hit, as will the cost.