I read a statement from the Magic earlier that they're not willing to trade Howard no matter what, so a Melo type midseason-trade may be out of the question. Howard also has a player option after the end of the 2011-12 season which he won't likely exercise. Ultimately, he could end up anywhere in 2012, it's all up to his discretion.
Some possible destinations in 2012-13:
LA Lakers: Lakers can still acquire Howard (max contract and everything) through a sign and trade. Orlando may change their minds about refusing to trade Howard once the writings on the wall that he wants to go elsewhere. It's still better to get value for him through a trade than to lose him for nothing in free agancy.
Celtics: Plenty of cap space
Miami: not possible, unless they trade one of their max contract players or Howard agrees to sign for the MLE.
Nets: Plenty of cap space if they don't acquire any free agents this coming offseason or if Deron opts out. The Nets may also soon move to Brooklyn which is a positive.
*About BLo, he's a player who was horribly exposed as soft and a very poor rebounder (6.0 rpg) this year. He's not as untouchable as one might think.