I have seen a few people lament that the Jets could have signed Derrick Mason and kept Jerricho Cotchery to have a Holmes/Burress/Mason/Cotchery depth chart at wide receiver. This really would not have been a great move, though. It sounds great on paper. In practice, it probably would have been counterproductive.
There are very few sets where four wide receivers play at once. The fourth receiver on the depth chart sees much more time in practice than on the field. Those reps are better served going to a young player like Jeremy Kerley instead of taking them away in favor of an upgrade at a position for a player who will barely see the field. It also would take away a roster spot from a guy who might help the team on special teams. Again, the fourth receiver would not see the field much in the passing game. Why not give a lower spot on the roster to a guy who can contribute consistently on special teams?
The fact the Jets have a tight end in Dustin Keller they can easily split out wide in spread formations only strengthens this point.