No team in their right mind is going to trade anybody of any value. If Howard doesn't want to play for the team he will sulk on the bench for a year and then go where he wants to in free agency.
If the Magic decide to keep him, Howard has to at least try a little bit just to maintain his value when he hits the free agent market.
If the Magic want to take the Nets trade, the one proposed a few posts earlier is pretty good. Lopez only has one year left on his contract and Brooks is still playing on his rookie contract. Humphries isn't currently under contract so the only wild card is what he would sign for.
Also, Rambo, I love you, but there is no way that Howard is a top 5 player. For last season he was 6th in PER and he barely makes the top 15 in Win Shares.
RFX, not sure if this is what you were asking, but if the Nets trade 3 first round picks to Orlando, the picks will be based upon the Nets performance in the years tied to the draft picks. Orlando's performance will have no bearing on those picks and will only affect the first round picks that Orlando had in the first place.
If the Nets to make the trade, it's true that they basically will have nobody under contract past Howard and Williams. That said, that is a pretty potent 1-2 punch. Given that they will play in one of the most desirable markets in the NBA, I don't think it will be that hard to recruit the talent necessary to compete in the East.