"Core iX" is an expression relating to the current crop of Intel CPUs. It refers to Core i3, Core i5 and Core i7 processors. It just means Core i-something.
What has changed lately is the introduction of the second generation of Core CPUs, named Sandy Bridge. While these keep the Core iX naming scheme, their model numbers are in the 2000's, for example Core i7-2600. This architecture is way faster than its predecessor.
No Apple product uses these new CPUs. Maybe the next MacPro's will use them, maybe not. We'll just have to wait and see. These CPU's are shipping outside of Apple-land, though. Got a new laptop with one and it's screaming fast.