FBX has been quite successful for 3d content. The format itself is proprietary but the FBX SDK is quite easy to use. Pretty much all tools support it and it pretty much completely solves a wheel that was being re-invented thousands of times per year. Now you can just export as FBX and move on with your life.

I'm not sure how FXG was every going to replace PSD given than FXG is for vector based graphics. I suppose it could replace PSD for some types of content but stuff like digital painting it doesn't seem appropriate at first glance?