TkGS is a project to replace XLEL to improve Tk's performance and cross-platform (or "device-independent", more properly) "maintainability". These enhancements might open up such new possibilities as a framebuffer-targeted Tk, themes support, graphical refinements including alpha transparency, ...
Another interesting aspect of TkGS that has been discussed is that it may make printing of graphical widgets easier.
What is the status of TkGS -- it looks like a wonderful idea, but I'm wondering if it is stuck... Nothing seems to have happened for a long time...
AK: AFAIK the only person working on TkGS is FB and he is constrained by real-life. I believe that he would be glad to have volunteers.