THE 975x works with the kentsfield quad-core, not the yorksfield quad-core.
The next gen chipset is called bearlake. That will come in the form of p35,g35, and x38. Some versions will have a 1333 Mhz front-side bus and DDR3 RAM. Bearlake will come in Q2-3 2007.
The next socket is Socket B and H.
Socket B - a new socket for future Intel CPUs incorporating the integrated memory controller and CSI (LGA 1366 contacts)
Socket H - a replacement to the current Socket T (LGA 715 contacts)
The first CPU offering from Intel to be on Socket B will be Bloomfield from the Nehalem family while the first 45nm processors from AMD will be based on Socket AM3
Socket B/H will come in Mid 2008
In short, if you just need the current quad-core, the 975x or p965 is good enough.