Specific notes in Mac OS X Mountain Lion's configuration files are hinting to an update for Apple's iMac and Mac Pro desktop computers. The files make note of unreleased iMac (iMac13,0) and Mac Pro (MacPro6,0) models, both of which are now expected to drop the optical drive altogether.
AppleInsider notes that Apple's Boot Camp Assistant "references the plist to display a listing of newer Mac models with EFI-level support for booting a legacy operating system from a USB flash drive." Of course, that is a feature already supported in today's models, but the explicit description suggests that Apple may be specifically targeting a bootable Windows 7 volume from an image file - and not a DVD anymore.
The file references disk drive free systems such as the Mac mini and the Macbook Air at the same, time which fuels rumors that Apple could be taking the step of ditching legacy optical drives. We know that Apple isn't shy of killing technology it does not believe or want anymore. It did so with the floppy drive in the original iMac. Back then, Apple already played with an "iDrive" as a cloud storage product in 1998, which did not work that well due to the lack of generally available broadband connections.
Given broadband speeds today, as well as cheap flash mass storage, it is not unreasonable to believe that Apple may be considering the departure from the optical drive. It would even support its business model in an effort to move its users to the iCloud service.