The new GNOME release will do away with icons on menu items and on dialog buttons. The exceptions are menu items which represent a dynamic object such as applications, files or bookmarks, and devices. This obviously means that the GNOME panel, as well as the panel menus, will still show icons for their items.
What is as of yet unknown, however, is whether or not this will get a GUI checkbox so you can switch back to the old behaviour. Since there are talks of removing the "Interface" tab from the Appearance tab altogether, it's unclear where such an option would go even if they wanted it in. Else, it will be a trip to gconf-editor.