According to Peter Gammons, who has some of the best insider information in the business, Willis and Cabrera aren't going anywhere.
Good. If the team is trying to poise itself for a run at the playoffs in the next year or so, they will need both players. Whether or not the playoff run will happen in 2008, like everyone hopes, will depend on how quickly the players who are injured recover. But if everyone is good to go next year, it could happen then, but given how rehab is going 2009 may be a more realistic target date.
If either Willis or Cabrera are traded, it will probably be for a boat load of prospects and if that happens, it could be several years before the Marlins can seriously contend.
I think they will both be with us until they are free agents if the front office thinks the team has a chance of making the playoffs.