We have VC, Lopez, and Brooks as trade assets.
I don't think that VC can be traded anymore. The Suns have until the start of the free agent period to buy him out, which will happen after the lockout is lifted, but while there is a lockout I don't think players can be traded. So it seems to me that trading VC is no longer an option. Also, the Suns were not going to trade him anyway. They can save $14M if they simply buy him out. That's a big figure for the Suns owners to turn down.
Aaron Brook is not really a trade asset either. He cannot be traded directly, he can only be a part of a sign-and-trade. For that to work a team over the cap would have to want him and he'd have to want to play there. But in such a case we probably wouldn't get more than a second-round pick in return (like we sent to Chicago for Warrick and Atlanta for Childress). This was discussed in another thread.
Lopez is the only viable trade piece the Suns could afford to part with. Dudley could also be dealt, but the team would probably be wise to hang onto him unless a really great trade opportunity materializes, which isn't likely. Pietrus' expiring contract may also be easier to move, but none of our trade assets are likely to bring in a starter-caliber SG.
So if we are going to add a SG, it will most likely be a FA for the mid-level exception, if it still exists. Due to salary cap the Suns options are already limited, and they are likely to be even more limited under the new CBA.
Of the free agents available, I'd probably give Marcus Thornton a look, but he may get bigger offers and is restricted. I don't care much for Afflalo. The Suns are going to need a scoring guard, and Afflalo is not known for his offense. I just don't think the Suns will be able to add anyone better than what they already have at SG this off-season. I'd much rather give Childress more minutes than to pick up another player of same caliber. Addressing the backup PG position will prove to be a more urgent matter, imo.