Though I really don't know if/when they are coming out, I would suggest you wait till after October if possible. AMD gonna probably be releasing their 2800+ by then, so they might update their mp's also. Plus mp prices will go down most likely when tehy release the new cpu. Thats what i would do.
I bought my dual mp 1900+ in may. By christmas, they will have single cpu's that reach the performance of my two processors. I wonder what there will be out by next May...