BGH,
There are a few names missing from your list. Perhaps you know if they have announced retirement?
Wayne Allard of CO
Thad Cochran of MS
Larry Craig of ID
Chuck Hagel of NE
John Warner of VA
In Virginia, it has been reported that John Warner has decided to retire, but will not announce his decision until later in order to help the candidacy of Northern Virginia Congressman Thomas M. Davis.
Allard has already announced his retirement.
Cochran, Craig, and Hagel are rumored to retire or run for VP(Hagel).