Blizzard have revealed the name of the huge content patch that precedes Wrath of the Lich King on the front page of their EU site: Echoes of Doom.
Going by today's announcement that WoW's Arena season 4 ends on October 14th, it's a safe bet that the patch will be released on the same day (a month before the expansion hits the stores), but as yet, the 'more details' link leads to the last content patch, Fury of the Sunwell. Stay tuned for more details.