Update will bring an end to the Dread Masters saga.
We already knew a lot about the upcoming 2.4 Update for Star Wars: The Old Republic, including that Warzone Arenas were being added. But now, BioWare is talking a little bit (emphasis on little) about the Dread War missions.
According to the official site, The Dread War Update will include a level 55 operation that sends players through the Dread Fortress, culminating in a battle with one of the Dread Masters. Players will then move into the Dread Palace for an "epic finale" to the Dread Masters story line.
If the new arenas interest you, then you'll want to check out the faux interview with arenas announcer Baron Deathmark. He sheds a few more details on the arenas, but not much.
The update is still listed as "Coming Soon," so we'll have to wait a bit longer to get any more information on what may be included and when it will be available.
Source: Official site