More specifically, not just graphics drivers, but all 32-bit KEXTs.
A KEXT is short for “kernel extension.” The kernel is the core of a computer’s operating system; Windows has a kernel just like OS X has a kernel. The kernel’s job is to do things like manage connected hardware and how it interacts with OS X, coordinating system resources when multiple programs are running, and other extremely low-level tasks that are typically of no concern to the end user.
I’m not a Hackintosher, so I don’t know for sure, but I suspect that the complete drop of support for 32-bit KEXTs is going to suck for them. Many of the hacks they use to get OS X running on non-Apple hardware come about in the form of KEXTs.