Six cores are still speculation as far as I've heard. But 8 cores have been confirmed by Intel. Anand and The Inquirer claim Intel says they want them out by 2010. I would add a 2-4 months to that as usually they're late.
There is no more speculation, intel confirmed through its road map that 6 core westmere will be appearing. So no 8-12 cores until Sandy Bridge, and actually no 4 core 32 nm products that aren't xeons until Sandy Bridge as well.