It is a common misconception that one should list as copyright holder for docs, sourcecode, etc. the name of the project, unless it is an actual legal entity.
Obviously, 99% of open source projects aren't legal entities. Likewise, Inkscape isn't and probably won't be a legal entity, so can't hold copyright.
Assigning copyright of something to a non-legal entity invalidates it. If there would ever happen to be any question of copyright, this would make it difficult to chase down who really holds the copyright. So ironically by trying to do something nice for the project it could cause more problems than it solves. Thank god that this is almost never ever an issue since open source projects rarely get into legal troubles.
Instead, list yourself as the author and copyright holder for things you make, and make sure to declare it GPL'd. (If you wish, you can dual license with yourself and Inkscape if for some reason you're optimistic that one day someone will bother to file the papers to make it a legal entity.) Also take care to provide good contact info so folks can track you down 10 years from now if, for instance, they needed to assign you a bunch of stock options or something. ;-)
Bryce