The first details of DMC4 have been released in Famitsu magazine in Japan. The biggest peice of news is that the unthinkable has happened:
Dante is not the main character. The player will in fact be controlling "Nero:" No, not Nero as in mistranslation of Nelo as in Nelo Angelo as in Vergil, but in fact a totally new character to the franchise.
Nero is a lot like Dante: he has white hair, wears a red vest and a long black coat, uses a big sword and a gun in each hand. He also has an ability tied in with his demonic right arm called "Devil Bringer" which is supposedly "Something the PS2 could not handle." He is confirmed to be significantly younger then Dante is. He is also a knight from a secret sect that views Sparda as a god and is questing to undo some seal of Sparda's when all of his allies are killed...by Dante. While speculation about Nero and who he is runs rampant, there is no more official information.
Capcom has stated that there will be a "Suprise" presentation at thier main stage on the last day of TGS. Playable Dante, maybe?
Head to the forums, people, and discuss. And see the Magazine Scans.