This was mentioned in on a mailing so I was compelled to go looking for a definitive source. From Universal Binary Programming Guidelines [pdf] (pg. 47), "Macintosh computers using Intel microprocessors do not use Open Firmware."
What are the ramifications of this? Will I be able to hold down the C key to boot from a CD-ROM? Will I be able to hold down the mouse key to eject media? How will I netboot? And, perhaps most importantly to me, will this mean Target Disk Mode is gone? If there's no Open Firmware, what is in its place? Surely not the unpleasant BIOS found on PC hardware. Despite the fact that shutting down is not often necessary and somewhat discouraged, the Mac boot process and its capabilities are an important part of the Mac experience and not to be trifled with.
If Open Firmware is going, what other parts of the Mac are going and why? Does using an Intel processor necessitate such changes? Are Macs going to have not just Intel processors but Intel motherboards with only minor changes centered around keeping OS X on Mac-only hardware?