I think there's another reason behind the decision. The new, non-removable battery.
They might have needed the space for the new battery. The ExpressCard doesn't only use up its own space, but space for the frame and connector. Looking at the difference in placement, the moved the SD further towards the rear. So, between that and some customer feedback they could thought the SD slot a good compromise between an ExpressCard and nothing.
It'll be interesting to see the take-apart on the new one.
Personally, I think a "pro" machine should have the option of an ExpressCard. It's used for more than just memory cards. I have the 17" UB, but I would feel restricted if I didn't have the ExpressCard option. Ironically enough, I keep a (ready?)
SD card reader in it...