Does ST ever announce a final date for new members?
 

From my experience the formal induction date of new members seems to be a secret with this alliance. 1W & * generally mention that a certain airline will join on a particular date, but with Aeroflot, NW, CO & KL it just seemed to happen out of the blue. I mean I knew they were going to join but did not have a specific joining date.

Not correct, actually.

SkyTeam announced about 3 months in advance both the Sept 15, 2004 joining date for KL, CO, and NW, and the April 14, 2006 date for AeroFlot. The announcements were by way of SkyTeam's web site, and the airlines themselves (web sites, inflight mags, etc).

Cheers!