Any chance they are doing 3x original iPhone rez?
320x480 = original
640x960 = Retina (2x original)
768x1024 = iPad 1 and 2
960x1440 = 3x original?
Interesting speculation.
Although that would change the aspect ratio of the iPad and make it the same as the iPhone... from a developer's perspective that could potentially cause UI design issues for exclusively iPad apps.