There is some much welcomed news on the five player dungeon front tonight. Zarhym has confirmed that there will be a new five player dungeon in an upcoming patch. That dungeon, according to Zarhym, will be comparable to Magister's Terrace.
No other information is provided on it, other than the promise for a preview when it's ready.
Magister's Terrace was released in Patch 2.4 and contained higher-than-normal item level equipment and weapons for players. Many people felt that Magsiter's Terrace was also the hardest 5-man dungeon introduced into the game at the time.
While there is no indication that this dungeon will be released with patch 3.2, I don't think it's a wild assumption to make. Blizzard has previously indicated a future patch will also contain a new battleground.