Sure, generally when Apple revs a product it ends up that prices go down. For example, if the were to introduce a 6 GB Nano, I would expect it would go for $249, and they would bump the 4 GB model to $199, and drop the 2 GB model.
But, the Nano was just introduced! I'd bet you'd wait 6-9 months for a new one to be introduced. So waiting is probably a silly idea, now.
If you want a good deal right now, go buy an iPod Mini on blow-out close-out.