@yokaiforte:
I'm not sure if this is true or not, but I remember hearing that Gold Roger gave himself up. If that's true, why would someone who knows his heritege give himself up to the "enemy"?
That's not confirmed, but it wouldn't be surprising if Roger were captured or if he gave up. He won in the end; by becoming a martyr for his ideals, his death started a massive frenzy that has even the World Government flustered. This leads me to think; what does the WG consider worse? The Great Pirate Age, or a new Pirate King? Assuredly, a Pirate King would bring an end to such a golden age, but note the folowing:
Some have theorized that Whitebeard, like the Shichibukai, has a contract with the WG. This isn't supported, but it's somewhat logical; why would the WG spend all its troops batting Whitebeard, when there are a huge number of individual threats? Assuming Whitebeard isn't part of the "D" connection, I could easily see the WG adverse to someone like Luffy becoming Pirate King, rather than a figurehead-like person such as Whitebeard. Sure, he's got Roger's power (or had), but since he's partially connected to the WG, they can partially control him.
On a final note, I doubt the kingdome's name would be "D". As Ivotas said, it would be quite early for so much of the mystery to be revealed, although one does suspect. Before I read that line, I was hoping Clover would give up some strange name (one that we had not heard before), making the "D" connection a bit more ambiguous.
I finish with a question. Marieoja connects to Grand Line at the second intersection of Red Line, right?