The [link|http://www.gnustep.org/|GNUStep] mob have Display GhostScript. I can't tell if this is supposed to replace X or run on top of it, though. Some pages suggest it will, others show X as part of the structure.
The [link|http://www.ggi-project.org/|GGI Project] is still trundling along, too. I'm not sure what they wanted to do to X, but I think it was "replace most of it".
Wade.