Digitimes, motherboard manufacturers have started shipping products based on Intel's X48 chipset into the channel a few days ago, so if you've been holiding off on making your purchase, the good news is that you won't have to wait much longer.
There's no official word from Intel about the X48 chipset as yet, and it doesn't seem like there will be an official launch event. Saying that, as this is pretty much just a new SKU of the X38 chipset, we wouldn't be amazed if Intel didn't bother with a launch event altogether.
The initial shipments are only minor quantities and large-scale shipments aren't expected to happen until next week or possibly a bit later, depending on the manufacturer. The question is how popular this chipset will be, especially with the very imminent launch of the nForce 790i chipset from Nvidia.