As of now, KG, Duncan, and Kobe are on that list. As of now, the order should go Duncan, KG, Kobe. Unfortunately, due to the huge hype machine of LA and the need for writers to constantly find the "next Jordan," Kobe will probably be ranked ahead of those two. If you ignore the fact that Kobe played in LA with Shaq while KG whiled away in Minnesota and Duncan was dominating in the little town of San Antonio, then I truly believe that in a vacuum, Duncan and KG have been better players to this point than Kobe. Kobe may move up on my list if he lasts longer than the other two, but we'll see.
Lebron, barring injury or steroid story, will definitely get there. Probably up to #1. Howard will make it. Wade might, if he can play at his peak without major injuries every few years. Durant and Paul certainly have the skills to get there, but we'll see. Don't sleep on what Durant is doing at such a young age. Ridiculous.
I don't think that Allen or Pierce get there. Nor does D-Will, or Nowitzki or Bosh or Nash or Amare. Doubt Rose makes it. Kidd, I believe, is borderline.