Guily had the chance to leave last season when his contract was set to expire. He choose to stay even though he knew he would be spending the majority of the seasons ahead on the bench. He does not strike me as someone who would love to fight for his place. I can't see how he would be an upgrade over Camoranesi. The only thing he has on Camo is pace and a better finishing touch.
edit: about Tevez. He would be a really good player, but we already have 4players that are similar to him: Del Piero, Palladino, Miccoli and Bojinov. He's not a guy that will bag 25+ goals for us. Plus I don't like MSI acting as his agent. MSI is too shady a company.