Keep in mind that not everyone uses Tango icons, not everyone uses gnome, and not everyone uses even Linux! What about users in Windows or MacOS?? This won't bring any unification for them for the most part unless they have Gimp or Scribus (maybe other apps), and not everyone is using them with Inkscape. So what's the deal?
Actually the purpose of Tango is exactly that.
From wikipedia: "The secondary aim of the project is a style that makes
applications look appropriate running on operating systems common at that time. ISVs providing icon artwork that follows the Tango style will find that their application does not look out of place on Windows XP, Mac OS X, KDE, GNOME, or Xfce."
This is a big reason why major cross-platform apps such as Firefox, OpenOffice, Scribus, GIMP, VMWare to name but a few have all adopted Tango.
I know it can sound like us pro-Tangoers are being rather pedantic, but there are payoffs here, and one of the big ones is platform consistency.
Joel