They'll come down in price, the cost of memory always does. I still remember paying £140 for 4MB of RAM, now I can get 4GB for about £20-30. Same with hard disks, I remember paying £1/MB, now standard drives cost a lot less than £1/GB. As technology becomes more mass-market and demands increase, the price comes down. As for when, that's more tricky.
Crucial's M4 is now about £1.30/GB and has already dropped by about 15% since I bought my drive less than a month ago. I reckon 2-3 years, less if demand picks up.