"Hey Siri" support and possibly wireless charging case alongside AirPower charging mat.
What We Learn From Leopard's Delay
A delay until October was actually predicted in a Page 2 rumor by DigiTimes. While Apple has claimed more broadly that the delay was due to a shift in resources to the iPhone project, DigiTimes said that the delay would be due to Apple's plan to "have its new OS support Windows Vista through an integrated version of Boot Camp."
While Apple has long-claimed that Boot Camp will ship with Leopard, and the latest version of the Boot Camp public beta did incorporate Windows Vista support, DigiTimes was careful to refer to an "integrated version" of Boot Camp in their story. This specificity was noted by Arn in a blog posting on the matter, suggesting that "integrated" Boot Camp might be something closer to Parallels virtualization.
None of Leopard's "Top Secret" features have yet to leak from Apple. However, this integrated version of Boot Camp which has yet to be seen in previous developer builds may point to one such feature.
While DigiTimes' rumor accuracy has been poor in the past, this is the latest in a string of stories from them to be corroborated (LED-backlit notebooks, Apple Notebooks with NAND Caching).