Those four are definitely the favourites.
Pietersen would have do do something phenomenal to catch up. Tremlett is an outside possibility, if he puts in another great performance he could end up with 20+ wickets at a sub-20 average, which would be seriously hard to ignore.
But if any of Cook, Trott or Hussey make another hundred they are nailed on.
Ain't nothing in the woodshed, except maybe some wood