I'm curious about the current state / roadmap / priority for linking SVG files in Inkscape.

This seems to be a reasonable summary of the current state:

https://answers.launchpad.net/inkscape/+question/97946

In brief:

1) <use xlink:href='file:///path/to/foo.svg#thing'/> gives an "Unsupported URI" warning, and no content. I think a <use/> linked to the whole doc. would be invalid, but targeting an element should work / works in Batik?

2) <image xlink:href='file:///path/to/foo.svg'/> gives the foo.svg page rasterized at 90 dpi according to the inches in foo.svg

3) <image xlink:href='file:///path/to/foo.svg#thing'/> gives nothing, perhaps it's invalid anyway.

4) there's no UI for creating <image/> links to .svg files, or for setting the aspect ratio to match the source, except the XML editor

For (2) keeping the vector data instead of rasterizing is a wishlist bug from 2008-1-5 (171795), and I'm not aware of any wishlist items for UI elements.

It seems to me that allowing links to other SVG files in this way would be really useful in many cases, but there seems to be little interest from users or developers, and I wonder why. Is there some obvious alternate mechanism I'm overlooking?

One use case which would make Inkscape particularly useful to the open-source map community would be linking to generated SVG map content so post GIS enhancements could be made and the underlying map(s) automagically updated. But I think there must be countless cases where this functionality would be helpful. Is it just a case of so many things to do and so little time?

Cheers -Terry