Intel is targeting to have the X48 chipset ready for purchase by the motherboard manufacturers come week 45, that's t he second week in November. These things can always slip slightly, but it looks like Intel's partners will have plenty of time to tweak the performance of their X48 products.
We're expecting a January launch alongside faster 1,600MHz FSB processors, as the X48 chipset has official support for this bus speed. Saying that, it looks as if the X38 chipset, or at least boards from Asus and Gigabyte already supports the faster bus speed.
Other features include DDR3 1,600MHz memory support and lack of ECC memory support, which shows that this chipset has been tuned for performance, since the X38 can be used with ECC memory for entry level workstation products.
The X48 chipset also lacks DDR2 support according to the information we've seen, something the X38 was meant to lack, but something that got added in the end, possibly because Intel realised that there wasn't enough DDR3 modules on the market in time for the launch.