Not "might" - will.

That's why there were separate "Mac editions" of certain cards (like GPUs) - the Option ROMs were different to support the Mac's frankensteined PPC OpenFirmware-like setup, and later to provide early EFI option roms when most x86-targeting cards were shipping with classic VBIOS.

EDIT: And while there was x86 emulator on many firmwares, it was often not enough to run everything, and x86 NIC firmware won't work for netbooting a PPC machine