This guy is about as well-trusted as it gets when it comes to internet rumor sites:
To put it simply:
Phoenix trades: Shawn Marion (doesn't get along with Amare, max contract), #27, possibly Barbosa
Seattle Trades: Rashard Lewis (Can opt out after next year), #10, possibly Fortson
Basically Phoenix does it to stay competitive for now while extending guys like Diaw, knowing that Lewis is likely a one year player.