Ram prices will continue to drop, and in fact, now that all the manufacturers can sell the Xeon 55XX series chips, I expect to see the economies of scale to help us with the prices. People are running DDR3 1066 ECC registered which seems to work fine (other than it appears to run hotter, requiring heat spreaders). I suspect a slight hit in latency, but nothing that will really be noticed. I have seen 4gb ecc registered dimms go for as cheap as $200 each. I think what that barrier is broken and we see prices in the $100-$150, many people will upgrade to 4GB configs (I am looking at 24GB for my dual proc. setup).
Peace,
Noushy