If you are talking about trading a suns player, think only of Kurt Thomas, Marcus Banks, & James Jones. I think they will have to trade their last pick to be able to dump Banks and his salary. (However, their last pick in this draft is going to be valuable, and they may get back a 2nd pick to go along with the player they get for him) They may not trade Thomas until the trade deadline next year when some team is having a bad start, and wants the flexibility of an expiring contract. The reason I think they will trade Thomas is because of the salary cap, and this frees them up to draft a couple players and keep the rest of the team intact.
Marion, Barbosa, Nash, Amare, & Diaw, are not going anywhere. The player up in the air for me is Bell. I do not think the suns will trade him, but they need a taller two guard that can really shoot. They may not be able to get one, and Bell will not be traded unless they do.
The trading down if Horford is not avaliable, is a viable option. They could trade down and get Brewer and another draft pick later in this draft or next years draft. (But they really need a guy like Horford to add size and flexibility to this team)
There is a chance they could draft Splitter with a pick from another team, or hope he is there at #24. With a lot of talent in this draft, Splitter could fall just because of the uncertanity with his contract overseas.
I do not think the suns will draft a point guard, they had two chances last year to get an excellent point guard and passed on both. Barbosa is going to be that backup combo guard and he is going to be better next year than this year!
I believe the suns will sign or draft a swing man this year for sure. They need one for flexibility for D'Antoni's system.