If the Magic don't trade DH12, they can offer him a 5th year which equates to $30m more than he can get from any other team on the FA market (which would be a 4 year deal only). Word is the Magic might be willing to gamble by holding onto DH12 and call his bluff that we won't leave the $30m or so on the table.
Now think about this; agents have a very big influence on the player's decision, and what agent is going to leave $30m guaranteed on the table? In 4-5 years, it's concievable DH12 won't be able to command another max contract. He'l be in his early 30's and have 12-13 years of wear and tear on his body.