A little more information has become available regarding Naxxramas in Wrath of the Lich King, which we would like to share with you:

Naxxramas is planned to be somewhat of an entry level raid dungeon in Wrath of the Lich King and not the hardest dungeon in the game, so things will be a little different from what they are now. One difference is that it will float its way back home to Northrend and will therefore no longer be found in the Eastern Kingdoms.

The developers like having content be more available to players and as such no final decisions in regards to attunement have been made, but the developers also like having special quest lines available to help players be more prepared to face raid dungeon content. It should be said that as an early raid dungeon, there isn't a big reason to block a lot of people from accessing it.

The challenges for hardcore players will remain though, because Naxxramas is a big dungeon that will not be easy to complete all the way through. The hardcore players can push into the higher content from there.

There is not yet much we can say to those of you who are already attuned to the current incarnation of Naxxramas. As mentioned above, things like attunement has yet to be fully decided, so it is still too soon to say if you will be required to go through attunement a second time, or if there are any plans to give titles based on the original Naxxramas attunement.

Those of you who wish to know if The Ashbringer will drop again will have to stay tuned for the next BlizzCast, where this will be mentioned briefly

Tier 3 Armors
We have already stated that we plan to re-use the armor models in the new version of Naxxramas as well so players will be able to get the look they wanted. For players who want the look and the stats of tier 3 armor at level 80, hopefully they are already farming the dungeon for them.