The Ilo Gallium3D driver developed by Chia-I Wu was merged into mainline Mesa back in April although it's an unofficial, community-maintained driver. The Intel OTC folks have nothing to do with this code. This driver also isn't to be confused with the more reliable i915g driver for old Intel hardware.
This weekend, Chia-I Wu extended the Intel Gallium3D driver into supporting Haswell. By looking at the code differences between the Ivy Bridge (Gen 7) and Haswell (Gen 7.5) code-paths in the i965 DRI driver where there is the official Intel open-source support, he was able to extend his driver into handling the latest-generation Intel graphics cores on the new shiny and fast CPUs.
Testing so far appears limited to Xonotic and some Mesa demos, so your mileage may vary if you try out the experimental driver. The commit adding the support can be found featured on Anzwix. I'll try testing the Ilo Gallium3D driver today and see how it's doing; stay tuned to Phoronix and my Twitter feed for updates.