Ok, my previous guesstimate didn’t really hit, as I guessed that Cataclysm should hit around October 1. A bit optimistic, eh?
Today Blizzard announced that the 4.0.1 public test realm was released. This is the patch that will hit the live servers before the expansion with the events that lay the base for the expansion’s delve into lore.
From the earlier expansions we know that the patch itself is live for about a month before the the expansion hits, and that the date has been annonuced about two months in advance. We also know that Activision’s CEO has promised a 2010 release. In general, having a release in December is not optimal as this might require people to work overtime during Christmas, you might miss out on getting under the Christmas tree, and so forth, so I guess Blizzard will release before that point.
I have no idea about how long time the patch will be on the PTR, but I would guess at least a month. Trying to copy a character today, I saw that the queues were full and that the estimated processing time was 6 days. It looks like they are going to get sufficient testers at least.
Let’s estimate that the patch will be on the PTR for just under one month. Then the patch has to hit and be live for about one more month before the expansion hits. Based on this, I would guess that the expansion hits on a week day between November 11 and November 25. All dates are plausible, but if I were to gamble on one of them, it’d be Thursday November 18. Let’s see if I’m closer on this guesstimate.