I truly believe that Boldin will be traded this offseason for a couple reasons.
From Boldin's standpoint, this will be his last big payday. With his style of play and history of injuries, Boldin's time of commanding a high dollar salary is fading fast. I don't think that this year will be his last productive season, but I do believe that they are numbered and Boldin knows this. His facial fracture this season only enforced this fact more and I am sure that he wants a huge contract and I can't blame him.
Unfortunately the dollars that Boldin wants does not make sense for the Cardinals organization. With a potentially transitioning offense, and multiple players to extend, I am sure that the Cardinals will be hesitant to sink considerable money into a depreciating asset like Boldin. I am sure that they will offer him a quality offer from their standpoint but I believe that it will not be in the level that Boldin is looking for.
The best part of all of this from the Cardinals standpoint is that they have all the negotiating power involving potential trades. Yes Boldin is unhappy, which can lead to a diminished trade value, but he is under contract for two more years so they aren't under the gun. Boldin also had a pro bowl season and had a career high in touchdowns to over-shadow his in season injury. Finally, the Cardinals had a very successful season which tends to inflate players trade value because it is a rare occurrence for players to hold out who are on successful teams. All reasons that if the Cardinals can't work out a deal with Boldin this offseason his value will have never been higher.