I've long felt that if there's ever a band that will break progressive death metal to the masses, it will be Opeth. They're the closest band I've found to stirring me the way Metallica did back in the 1980's, and after nine (!) albums, they're getting even better.
Some food for thought:
Metallica - Master of Puppets
1986 - Billboard - Position: #29
1986 - UK Albums Chart - Position #41
Opeth - Watershed (praised by the NY Times, Pitchfork, Blender, AMG, etc, reaching 88 on Metacritic)
2008 - Billboard - Position: #23
2008 - UK Album Chart - Position: #34
2008 - Finland - #1
2008 - Sweden, Norway & Australia: #7
Not that I'm predicting anything. I'm just sayin' that Watershed is, I hope, a sign of things to come.
p.s. I'm really looking forward to Death Magnetic too, by what I've heard so far. It's been over 12 years since I've been able to say that about a Metallica record.