When looking at the member list for the new Fort Minor forums, you can see certain already confirmed collaborators with a post count of one thousand posts. These people included Mike, Jay-Z, Black Thought, Common, Lupe Fiasco, Holly Brook, John Legend, and Styles of Beyond. Meanwhile, there are other non-known artists with the same post count, such as Sixx John, No Warning, Bobo, Jonah Matranga, and the rest of the members of Linkin Park.
While this is unconfirmed, it's a major coincidence that all of these other forums members who are musicians have one thousand posts as well. It seems like a clue.
From what we can gather on these artists, Jonah Matranga is a soft-rock, bluesy musician. You may notice Sixx John as an underground rap artist from the soundtrack to the True Crime video game. We're unsure who Bobo is, although there is a DJ Bobo who is a reknowned composer, producer, writer, and singer who's been around since the early 1980s. More details to follow.
Check out the official Jonah Matranga site.
We stress that you please treat this as a rumour.
Thanks to Magdalena and LordBobness on the Fort Minor Forums.