I suspect this is because the iPad (4th generation) and iPad Mini were originally intended to release with iTunes 11, before the Novemeber delay. The back of the Mini box says that it requires iTunes 11 to sync correctly. I am not sure about what the back of the iPad (4th Generation) says, but I imagine it is the same.
As to why the current version does not have icons for the new devices: iTunes 10.7 (the current version) was released on 9/12/2012, which is way before the iPad Mini and the 4th generation iPad were released or even announced. Various people (and rumor blogs) will dig through the iTunes source code looking for these icons trying to find unreleased devices, so I suspect the icons are missing so as not to give away the new devices before they were announced on Oct 23rd.