Only three ways I know of that could speed up access times on the mechanical side ... Multiple heads per platter (i think we've been crying out for them, like... forever), and due to the higher density of these new drives, make the platter smaller with a faster spinning spindle... which is basically what SCSI drives and WD Raptor range do, 2.5" platters in a 3.5" case with 10-15k spindles.
A fourth method might be to store the allocation table (not entirely sure what to call it) in flash memory, rather than on the platter, but you'd need about 2-4GB or more of flash memory - depending on the total size of the drive, but storing it in flash means that the drive doesn't need to keep accessing it on the platter for every file, reducing track swapping.... but from my limited understanding, the allocation table placement and such is handled by the file system and/or OS, rather than by the hard drive itself.