The Broadwell PCI IDs have been added to Intel's Mesa DRI driver today, but they are still disabled by default with the 3D driver considering Broadwell to be "preliminary hardware support" at the moment. A few more important pieces of Broadwell hardware support still have to land inside the Intel Mesa driver ahead of Broadwell's CPU debut in the coming months.
While it's hard to gain much from the PCI IDs since not all of these IDs will likely end up being used in products going to market and the "GT" generation information isn't always too useful, the Broadwell GT1 PCI IDs include 0x1602, 0x1606, 0x160A, 0x160B, 0x160D, and 0x160E. The Broadwell GT2 PCI IDs for graphics include 0x1612, 0x1616, 0x161A, 0x161B, 0x161D, and 0x161E. The high-end Intel Broadwell GT3 PCI IDs include 0x1622, 0x1626, 0x162A, 0x162B, 0x162D, and 0x162E.
The Broadwell graphics processor PCI IDs were added with this Git commit. I'm extremely excited for Intel's Broadwell processors and they have great hope at the moment. As soon as they are released you can expect many Intel Broadwell Linux benchmarks on Phoronix.