Brolin in Men in Black 3?

His exact part is a matter of discussion, but in recent days there’s been chatter in Hollywood development circles of a few possibilities: He could play a new single-monikered government agent, with Tommy Lee Jones’ Agent K passing the baton to Brolin’s character. Or he could play Agent K as a young man. Or something else entirely.
Whatever the part, Brolin could be playing against some star power: Will Smith is expected to return in the new “MIB” as Agent J. Sony is currently contemplating a production start for the picture in 2010 (though it has yet to be greenlit). Is this possibly a recipe for something good to actually make the third one, if it ever gets greenlit, worth watching? Or is this just one huge failed attempt because of the plain fact that Will Smith is not even on board? Mind you, Men in Black 2 came out in the summer of 2002, so plenty of time has passed for the I Am Legend star to loose interest.