Taiwanese blog Apple.pro reports (Google translation) that Apple is developing larger versions of the MacBook Air, speculating that a 15" version could be in the works. The report provides little information other than that the new MacBook Air would be based on new ultra-low voltage Core 2 processors from Intel, but they promise that more information will be forthcoming in the second half of this year.
Apple.pro's mixed track record includes genuine leaked photos of the current generation of the MacBook Pro and MacBook, but their purported MacBook video leak was questionable at the time of posting and did turn out to be false.