I agree, probably no SuperDrive in the bottom end.
Many users have no need for the SuperDrive at all and this is maybe $300 increase in the build cost over a CD-RW/DVD ?
Sure, if you have a digital camera and want to make your own movies, having a SupreDrive is great, but if you are working in an office where the backup procedures are already set up, this is probably not a necessary piece of hardware (on the other hand, if you do not have a backup procedure, the SuperDrive pretty much beats tape all hollow if you user DVD-RW given the cost of tape machines these days)
On a $1800 price point, Apple cannot reasonably be expected to fold in that extra cost.
What I suspect we may see of the other hand is offering the SuperDrive across the pro desktop product line as a BTO option (as opposed to the current limitation to the 867 and dual 800).