All of the icons that OpenOffice.org installs into the icon theme contain the version number - e.g openofficeorg-19-base Icon names should really be long term names as they will be referenced by other apps. e.g. because the OpenOffice.org launchers are on the default panel, the icon name is referenced in the panel configuration. So, when OpenOffice.org goes to 2.0 and the icons become openofficeorg-20-base, you won't see the icons on the panel anymore.
"by other apps", or "by panel"
In practice, its probably only the panel that references these icon names - but you could imagine some other app wanting to display an openoffice icon, using the name openofficeorg-19-writer and then finding it breaks later ...