Ok, so I took a few minutes to gather some rough data about how long the previous expansions were in the different stages of release, and I think it's interesting to look at.
So lets take a look and see if we can't draw some parallels from the context of these charts. See what I did there? Oh man I love cheezy jokes.
First up is the Burning Crusade.
Next up is Wrath of the Lich King.
And here we are with Cataclysm. I'm taking a rough guess as to the release time here, seeing as the two previous expansion packs required 5 months of development after the Alpha.
Or, this could mean that Blizz is actually getting the Beta testers in there so they can actually get feedback on things sooner (something tells me this is probably not the case).
The data seems to boil down to this: Cataclysm will more than likely be released after the 5 months of additional development, which happens to coincide with Blizzcon (Surprise!). They'll use Blizzcon to hype the crap out of the game and release it right afterwards and sales will skyrocket (as usual with Blizzard products).
So here's my prediction: Cataclysm will be released on October 26th.