You can read it on MMO-Champion here, the third wing of Icecrown Citadel has been officially announced to open 2 weeks after the second one (aka the 19th of January). By the way the next arena season 8 date, which will be the last for Lich King, has also been announced to be probably on the 26th of January.
The third wing of Icecrown will be the last before Sindragosa and Arthas, so we can expect to see the Lich King live the 2nd of February if they keep with the 2 weeks gating time period. Not that I expect my guild to go that fast (we're just finishing with the entrance wing) but I'm sure all hardcore, or even semi-hardcore guilds will keep up with the pace for normal mode.
Now remember that the last bosses of each wings also have a limited number of attempts you can have on them for each week. This number has been increased from 5 attempts to 10 though, so this week everyone will have 10 attempts on Professor Putricide.
Cataclysm release date thoughts.
Now I'm sort of wondering if ICC will be enough content for players until the release of Cataclysm, even with the artificial increased time need to finish the raid that this gating system creates (pool about that topic on the right side). More than 3 months between a raid is cleaned and another appears is usually too much, but if we have the same "new talents live test period" as we had at the end of The Burning Crusade we can probably add about 2 months to this 3 months period farming ICC.
Still 5 months lifespan only bring us to early July, and I don't think now that Cataclysm will be out before the summer (though I was thinking June before). Blizzard won't release during the summer, which brings us to a fall release.
Now you can understand the announcement by Blizzard about a new raid being given to us before Cataclysm launch. I would expect just before or just after they give us the new talents trees. A new raid adds about 3 more months to the time that can go before the launch without players quitting "en masse" the game. Which brings us to the fall/late fall release that seems to be expected by most people now (preorders even give an early November release date).
What do you think about it? I'm really eager for Cataclysm myself, and would like to see it before summer, even if it probably won't happen I'd like to at least see the "new talents live test period" at this time. The global revamp of the talent trees is what I want to see the most right now, I think the "old model" has done its time.