Hi,
Recently I have toyed around with Karl's gtk gui, and it is indeed not too far from being a replacement for the tcl/tk gui, but just changing the widget set doesn't really make up a new gui.
Therefore it would be necessary to design a new client server interface for the gui within pd.
This is definitely doable, if you know your way around in the pd sources, and what is more important should be done as an extension to the existing tcl interface.
Miller would certainly accept a solution like this to be added to pd.
... there is one thing left to really think about, which is the new data visualization, array drawing and the like, which might not be that easy to be cleanly seperated from pd's core code ...
Well, I currently don't have the possibility to put time in such a project, so I decided to fill in the last gap's in Karl's gtk++ gui.
Guenter