You are wrong.
Roberts was named to replace O'Connor.
Rehnquist died.
A second opening then occurred and Alito will be replacing Rehnquist. Roberts was elevated to Chief Justice and O'Connor agreed to stay on a bit longer is immaterial.
From a conservative's angle, Alito is replacing Rehnquist (2nd nominee, 2nd opening) and Roberts replaced O'Connor (1st nominee, 1st opening).
From a RAT's point of view and the MSM, ALito is replacing O'Connor since it makes the RATs' fight carry a bigger punch.
Judge Alito just said thank you for nominating me to replace Judge O'Connor.
No, you are wrong. After Rehnquist died Roberts was shifted to his seat. The successor to O'Connor's seat again became open. Alito has now been chosen to fill it. O'Connor will step down from the court as soon as he has been confirmed. Alito is replacing O'Connor.
That's reality, and it has nothing to do with either conservatives, liberals or the moonpeople.