Nothings been said what AMD are doing when SB hits. I'd imagine the current dual, tri and quads will stay the same but the X6 would most likely drop $30.
When LGA 1156 came out, prices of LGA 775 quads held firm. In fact, they're still where they were when 1156 was introduced. The Q9550 is still ~270 USD and the Q9400 around 205 USD.
I would expect slight price drops from AMD, just to remain competitive, but don't expect Intel to lower theirs.