The problem this year has been the hype leading into the season. We should have seen problems from the start with the lack of a capable point guard being able to take charge of most of the ball-handling and keeping the ball out of Wade and James' hands for the most part.
As for a trade, the best they can probably get would be Nene Hilario or maybe Greg Oden if they want to take that risk. It's still too early to decide if the Heat want to cut some of their losses with a trade over the off season. If the team struggles in the post season and don't even make it to the conference finals, then I'd have reason to believe that Miller or Bosh will be traded. They've been the two core players that have been lacking, I understand Miller's injury, and it's set to be either them or Spoelstra to go first.