Yes...the title "icon" is not the same as being "trendy and hip". You really think Nicole Richie or Sienna Miller will be copied in say, 5,10 or 50 years time? No, because they were not invidual. They might have a great style, but it's not new. The fact that they are styled by stylists is not the thing that disables someone from becoming an icon, but the fact that these women are styled copying someone else. Even Audrey Hepburn had stylists or people helping her, but she is an icon because that particular style is most remembered as her style. Now, most of today's celebrities/wannabe icons, no matter how greatly dressed, aren't original, or the ones that you mention to describe a look because fashion of today takes most of it's inspiration from old/vintage/retro/you name it things. Fashion is not "new" anymore, it is quite recycled. I'm not saying this hasn't happened in the past decades too, but in those times there were also "new" things. That's why most of those "icon" titles belong to people before the it-girls of today. Even Kate Moss is partly just a follower (she is an icon on her own right too, yes, but she owes a great deal to the older icons).
We won't be having many new icons if fashion is not going to start discover brand new things, not just take cool retro things and add a modern twist. I say that the 2000's will be a very dry season to get new style icons.
Then again there's this thing about people, who "are their own person" and exciting characters style-wise, like Chloe Sevigny or Sofia Coppola, but their style still is a reminiscent of the old icons. What should these kind of people be called? Or are they just mass?
I hope this didn't sound too complicated. English is not my first language so there also might be some strange phrasing...let me know if you don't get what I'm saying.