Men In Black 3 Could Start Filming In 2010

Looks like will be getting a third Men In Black movie.  I do wonder how many people are aware that it actually started out as a comic book way back in 1990.  The Hollywood Reporter posted that Sony has put "Tropic Thunder" writer Etan Cohen to write the script.  The plan is to begin filming in 2010, possibly as early as the spring.
 
Since the first two films were such blockbusters, this seems like a no-brainer, right?  The thing is, neither Will Smith nor Tommy Lee Jones have officially signed up yet.  Apparently Smith has stated recently that he would be interested in returning to the role of Agent Jay.  MIB2 was released back in 2002.
 
Is the time right for another sequel?  The two movies have earned a reported 1.1 billion dollars worldwide.  Salary could be a factor in getting both Will Smith and Tommy Lee Jones to commit.  
 
Could the movie succeed without one or both?  I enjoyed the first movie.  I could be wrong but I'm not sure if I've actually seen the second movie, as crazy as that sounds.  Are you looking forward to some more government-chasing-aliens action?  Maybe if they can't get both actors to return, Sony should give me a call.  I do have a black suit and shades...