The logic behind Pachter's prediction is that Sony and Microsoft will be aiming at the casual consumer with a less expensive device. He also predicted that the Wii U would ship without a hard drive at all.
Microsoft originally launched the Xbox 360 with two SKUs, one of which had no hard drive that sold for $199. That resulted in stellar sales of the 360 (even leading to shortages).
It's not unreasonable to think that the current manufacturers will try the same tactic.