Maybe they won't drop the price of the "Classic" PS3 (80 or 160), and instead just have the slim come out cheaper? They could position the latter as the poor man's PS3, and the older versions as still being "Premium"--by the chassis alone, unless there actually will be some lost functionality.
They'd have to be crazy to do it, but, if anyone would, it'd be Sony. They've been pretty damn reluctant to lower the price-tag on the fat ones.
I think it might actually move more PS3 Slims if they marketed it as "cheap," and they'd be able to not lose any more money on the fats.