If this processor was going to be released in the summer, they would say Q3. So the very fact they are saying 2H means they really mean Q4. Unless there are some rabbits in the AMD hat, I doubt Istanbul will be all over a Nehalem-EP dual setup, or 6 core Dunningtons.
Anyway, good luck AMD in getting this out. I like to see a bit of preformance and price pressure applied to Intel.