I could actually see Carmelo going on the market and we'd certainly have a shot at him (I personally wouldn't want him).
Not a huge market of available wings out there. Others who would be an upgrade and might be attainable:
Danilo Gallinari -- Last year of his contract, shouldn't be too expensive and really fits a need.
Tyreke Evans -- Not a perfect fit (doesn't shoot the three that well), but can create shots. Would be hard to get, but if NO doesn't expect Eric Gordon to play a full year, a defensive oriented SG like Avery Bradley, plus Turner, Sully, etc. could have some appeal.
Bradley Beal -- A SG, not a SF, but good size for his position and an upgrade on AB. Seems like the Wizards aren't crazy about the idea of giving him a max extension.
Markief Morris -- Can he play SF more or less full-time? His twin brother could.