The current high-end resolution for laptops is 1,920×1,080 pixels […]
Not really. I’m working on a 1920×1200 MacBook.
Even if Apple trades up to a much higher resolution than any other laptop but still manages to keep things readable, that would mean resolution and screen size alone would no longer give you a fixed idea of what content (Web sites, games, photos, etc.) would look like on a laptop screen. This could make comparison shopping confusing, and it would be another example of different computer manufacturers using different standards.
Why of course, Apple is in the business of ensuring maximum ease in comparison shopping.
We typically use the word resolution to mean something like 1920×1200, but that’s wrong. 1920×1200 is a pixel format; resolution is pixel density, like 300 ppi. With that said, pixel format and screen size is not what determine how images and text look on a display. To some extent they do since we hardly change the DPI settings in our operating systems. And that DPI setting, a resolution setting, is what really determines how things look.
A 1920×1200 17-inch display sports a 133 ppi resolution. Let’s assume the DPI setting in OS X is at 133 ppi. Now if Apple decides to equip the 17-inch MacBook with a 3840×2400 retina display. The DPI setting at 266 ppi will show images, texts, etc. with the exact same size on both displays. The only difference is the Retina display 17-inch MacBook will have images and texts that are as crisp as those on the new iPad.
A Retina Display would likely need more power, which would lead to either a bigger battery (and thicker chassis) or shorter battery life, or both.
Consider this: The MacBook Airs do not have optical drives. There is the possibility of an optical drive-free MacBook Pro. That leaves a good chunk of space to add more battery. A bigger more efficient battery, yes. A thicker chassis, no. Shorter battery life, no. Both, definitely no.
But, I have to admit, in many years of reviewing laptops, no shopper has every told me he or she wanted a screen resolution higher than 1,920×1,080.
I’m so glad, thanks to Steve Jobs, Apple doesn’t conduct focus groups to find out what customers want.