I don't think he'll come here, because there really isn't any need for us to sign him. I can understand that some may feel we're needy at the moment because Vidic is out, but once he's back ,Cahill would be deemed redundant.
Not only would he be behind Ferdinand and Vidic in the pecking order, he would also be behind Smalling, and possibly even Jones. He may be a decent defender, but to be honest, I think that some overhype him to an extent. He's another footballer who receives a lot of praise because he's good on the ball. His defensive ability is okay, but it's nothing so special that would warrant him being linked to nearly all of the top 4 contenders.
I can see him going to Chelsea now. Out of all of the top clubs, they're probably the ones who need a centre back the most. I think that they could get better than Cahill, however he is probably the safest option to take. It says something when you think that Cahill would probably be their best centre back if they were to buy him. Either way, I'm sure he'll leave. Coyle is coming out and blatantly admitting it, but he is hinting at it. Usually, even when a major player at a club leaves, the manager will be insistent in keeping him until the sale itself, or will appear that way. That doesn't seem to be the case in this one. Coyle is certainly hinting that he may be sold, which makes sense considering his contract doesn't have a lot longer left to run.