The latest issue of the Official Playstation Magazine has just been released with an in-depth look at Fight Night Round 4.  In it, the game is discussed along with what appears to be the latest confirmed roster for the game:

According to this issue, the roster will include the following:

Mike Tyson

Muhammad Ali


Ricky Hatton


Ray Robinson


Thomas Hearns


Miguel Cotto


Shane Mosly


Jake Lamotta


Marvin Hagler


Roy Jones Jr.


Carlos Monzon


Jermaine Taylor


Kelly Pavlik


Manny Pacquiao


Pernell Whittaker


Julio Caesar Chavez


George Foreman


Joe Frazier


Lennox Lewis


Ray Leonard


James Toney


Roberto Duran


Marco Antonio Barrera


Amin Asikainen


Paulie Malignaggi


Kermit Cinteron


Eddie Chambers


Arturo Gatti


Corey Spinks


Tommy Morrison


Sergio Mora


Fernando Montiel


Jorge Armando Arce


Anthony Mundine


Emanuel Agustus


Vinny Paz


Vivian Harris


Billy Dib


Diego Corrales


Erik Morales


Nate Campbell


Ronald "Winky" Wright


Yuriorkis Gamboa


Nonito Donair


Arthur Abraham


Joe Calzaghe


Roberto Guerrero


Edwim Valero


Victor Ortiz

The article goes on to say that this roster could also come by way of Downloadable Content later on.  Either way, those are 49 boxers in there that the fans can expect to play as.  Some new faces to the roster are Joe Calzaghe, Jorge Arce and Arthur Abraham among others.  Other important points from the article are:

• Speed and fluidity are two of the most noticeable aspects of the game engine.

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  “While taking any of the 49 real world boxers in the ring will be the initial draw, earning your own name will be possible with a hugely expanded Legacy mode. First, why not import your own beautiful visage into the game courtesy of the Photo Game Face, apply a signature punch, and choose from one of the seven basic boxing styles. Now the road to glory starts as a prospect at the Amateur Tournament where you'll start to earn respect. It's possible to drop a rank - to Bum - if you're a perennial loser, but the goal is to step up to club fighter on the path to Legend. You do that by identifying boxers you want to fight, scheduling the bout (or accepting and incoming request), and training like you mean it. You can undertake the training regimen yourself as it's all geared to improving your in-ring moves and punches."
  
  

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  "Working up that ladder, you'll see your abilities in a vast number of different stats improve, allowing you to cherry pick the perfect opponents to improve your ranking."
  
  

• Face buttons are used for signature moves, clinching and illegal moves.