Acceleration Architectures, state of the art.

Those manufacturers may account for nearly all PC/x86 type machines, but that is not the whole X space. Modern ARM chips, as used in things like smartphones, and soon to be seen in netbooks, now have 3D graphics cores in them, such as the powerVR from Imagination in Cortex A8-based CPUs. This looks likely to be a non-trivial fraction of devices in the future, so X shouldn't be ignoring them, although my understanding is that Imagination are about as helpful as nVidia when it comes to free drivers.