There is only a slight chance Oden or Durant stays for another year. That's two.
If you look at the very best teams, how many players come from them might depend on how far they go. A team winning it all and sticking together, like Florida last year, is rare, and even a deep run can convince guys to come out.
Florida: Horford, Brewer, Noah
UNC: Hansbrough, Wright, Lawson?
UCLA: Collison?
Kansas: Wright, Rush, Arthur
Georgetown: Hibbert, Green
Then add Al Thornton, Yi Jianlin, Acie Law, and you basically have a lottery right there, minus one or two players (Rush projected later, etc.). And that's not accounting for Tiago Splitter, Marcus Williams, and guys like Aaron Gray, who some team will take too high. And it doesn't account for Thaddeus Young, Javaris Crittendon, and other underclassmen who will probably stay in.
That's pretty amazing. Unfortunately, the Spurs are about 8 picks out of making any real hay, but will make for an unusually intriguing draft.