We're not sure this is still relevant -- the patent was filed in May of 2006 -- but the USPTO has just published a patent application from Apple
detailing a number of different 8cm to 12cm optical disk adapters. The application, credited to Tony Fadell, chief of the iPod division, says that since most software doesn't take up all of the available storage on a disk, it would be cheaper and simpler to use the 8cm disks when appropriate -- but that having to ship a standard adapter for slot-loading drives reduce any costs, because they're the same size as 12cm disks. The solution is to make the adapters smaller when they're not in use, and the filing goes on to detail several different folding and multi-part takes on the idea. Considering that such an adapter would make things slightly more complicated for the vast majority of Apple's all-slot-loading installed base, we can't see these ever actually shipping, but it's still an interesting idea.