Ummh.. Not really. E.g. first low-end unibody MBP was 1999$ but is/was available for 1349$ through refurb store. I don't know its refurb price when it was the current gen but the price dropped at least 500$.
They have to be cheaper than the next gen refurbs will be or nobody buys them. Low-ends doesn't drop down as much but high-ends do because next gen usually offers better performance for lower-price so they again have to lower the price so somebody buys them.
Hard to say how much but I can see high-ends dropping 20%, low-ends probably near 10% from current refurb prices
Yes, the older versions will drop in price, but they also get harder to find as Apple clears out stock, so it's sort of a gamble. If you do see a real deal (like an older model 15" MBP for $1349), grab it immediately, because it will be gone in no time.
I had a 17" refurb before the price drops(swapped it out for a new one) before the new models came out it cost me $2399 and afterwards it only cost $1949.
It was 1999$ as NEW, not refurb, possibly around 1700$ from refurb store when it was the current model but after the new models came, its price dropped to 1349$. And I mean when the new models came to online store, not refurb store.