But others predict that Apple will start the shift to Retina sooner, perhaps as early as October.

Yesterday, Richard Shim and Jeff Lin, analysts at DisplaySearch, said that their supply chain sources reported that production of 2560-by-1600-pixel resolution 13.3-in. displays would start in the third quarter.

"Our sources indicate that Apple will use this panel in a MacBook Pro unit to be launched in the fourth quarter [of 2012]," Shim and Lin said in a . "Production volume is expected to be roughly twice that of the 15.4-in. MacBook Pro."

They estimated that the year's production of the larger display -- the one used in this week's Retina MacBook Pro -- would be less than two million units, putting a sales cap on the new laptop.

It's also possible, however, that the higher-resolution 13.3-in. displays could end up in the higher-end MacBook Air, which uses a screen that size, too.