I just don't see Apple implementing a 2 hard-drive computer. It's not their style to wander out of "keep it simple" territory. To tech nerds like us it sounds like a great idea. But to old lady Stevens and Joe the plumber, it's confusing. Apple likes things clean and streamlined. A laptop with two drives in it goes way against that mantra.
Apple's been showing love for SSD+HDD combos as a CTO option in 27" iMacs since last summer.