wcarcass wrote:Uff... the ones just come to my mind, keyboard shorcuts, color profiles, path recognition, layer recognition, effects recognition, menu bars (logic, use, paradigm), ....etc.
Well, it's like this.
The teams see each other every year at Libre Graphics Meeting. Some things are discussed like e.g. OpenRaster file format (this year we even had an Adobe guy at the conference). Some things are possible to do together. E.g. all these apps already read system directories for color profiles (sadly, most recent spec coming from XDG is not supported by GIMP yet). Other things are
possible and specified, but not implemented yet, like e.g. reading swatches or gradients from system directories that is supported by Inkscape and Scribus, but not by GIMP (you can fix it yourself by adding a new path in Preferences). There is a Bridge-like application slowly coming to help getting this mess organized.
I don't understand what exactly you mean with path recognition or layer recognition or effects recognition.
GIMP, Inkscape and Scribus can read each others SVG files. Both GIMP and Scribus do not support SVG filters. For GIMP this is something that is likely to change as soon as it moves to GEGL which supports SVG beyond paths with flat fills. For Scribus this isn't something that is going to change any time soon unless some new dedicated developer starts working on that.
Scribus doesn't read XCF and doesn't have to. For multilayer images we already have TIFF (supported by Scribus, including clipping paths) and OpenRaster (sadly, not supported by Scribus and Inkscape yet). Inkscape can export XCF with layers.
I don't see menus changing a lot any time soon. I rather dislike Insert menu in Scribus, but I have a suspicion that there is very little we can do here, because Scribus team is a bit stubborn when it comes to changes like that

Besides both Inkscape and Scribus deal with objects, whereas GIMP deals with selections, so GIMP will never have e.g. Objects menu or Insert menu, and it won't ever have a Page menu.
More or less same thing applies to keyboard shortcuts: the apps have different sets of tools, and some tools are really implemented differently and will continue to be implemented differently. I can see how Scribus could be more Inkscape-like regarding all the drawing tools (in fact, I dream of a day I could stop prototyping layouts in Inkscape), but I can't see how GIMP can suddenly gain e.g. a tool for inserting an image frame. So you can have logic and shortcuts compatibility only up to a point. Few years ago I even maintained a comparison table for shortcuts. You can find it
here.
If I was a C/C++ developer first thing I'd do is bloody well rewrite all the drawing tools in Scribus and get rid of the junk like separate Line drawing tool. Unfortunately (well, not for me

) I'm not a programmer.
Finally there is a question of being able to work on same document in multiple apps at once. There used to be a project to deal with this. It's called
Verse. The project is abandoned. I spoke to its past developer few weeks ago, and he told me he would do things differently today. As a matter of fact GEGL, new GIMP's engine, can share its buffers, so in case Inkscape and Scribus ever move to GEGL (there are such plans for Inkscape), it will be possible to share a lot of stuff. But this is a lot of work, and even GIMP itself doesn't make a full use of GEGL yet. The only reason to hold a breath here would be if you were the person to implement all this

Let me know if you want more information on anything.