There's already been Haswell compiler support patches, but for the open-source graphics drivers there will soon be the first bits of public code. The Ivy Bridge Linux support code is mostly all molded into shape, so some attention has already turned to the Ivy Bridge-successor Haswell.
The upcoming Haswell driver release isn't totally surprising seeing as the for the Sandy Bridge and Ivy Bridge hardware the open-source code appeared about a year in advance and then publicly matured over the succeeding months.
I'm told that the Haswell Linux driver code will be out as soon as this week -- at least mode-setting is working on Haswell right now but the Intel Open-Source Technology Center is just waiting on the formal sign-off to release the code.
The DRM/KMS updates for Haswell should hit the Linux 3.4 kernel, the Mesa DRI driver support should be there with Mesa 8.1, and the xf86-video-intel DDX driver support for its 2.18 release. By the time Haswell hardware is actually shipping in 2013, most distributions should see "out of the box" support for the next-gen hardware.
The Haswell micro-architecture builds upon Sandy/Ivy Bridge with its 22nm process and 3D tri-gate transistors (shown in Ivy Bridge) while adding in Advanced Vector Extensions 2 (AVX2), a new cache design, proper Thunderbolt support, low-TDP models, and more. The graphics unit on Haswell is expected to be Direct3D 11.1 and OpenGL 3.2 compliant.
Sandy Bridge has been quite impressive performance-wise for being Intel integrated graphics, but with Ivy Bridge this performance is going to be upped substantially (as much as twice as fast as Sandy Bridge). This will happen again with Haswell where I'm told its integrated graphics should be comparable to a mid-to-high-end discrete GPU. There's stacked memory and some other graphics hardware improvements that should make Haswell Linux graphics even more interesting.
Stay tuned for the Haswell open-source code push when we can dig through the patches for more information. It's too bad that meanwhile AMD is still missing open-source support for already-released hardware (the Radeon HD 7000 series).