As anyone that followed Blizzcon 2007 knows, Naxxramas is being redone as the entry 25-man raid dungeon for Blizzard's second expansion, Wrath of the Lich King. However none of the other older dungeons are planned for an update according to a post from Bornakk.

One of the main reasons Naxxramas is being updated is because it fits so well with the atmosphere and story for Wrath of the Lich King. We understand that updating old raid dungeons could be fun for some people, but having level 80 players enter a bug infested desert doesn't fit too well with Northrend.

It is always possible that dungeons get updated in the future, but instead we are primarily focusing on brand new content for all of our players to enjoy.

Read the original post here.