No chance he joins Utd at all. Wenger is nice and calm about the whole thing for a reason. He's just sitting and waiting until Fab decides he's moving, then taking him back.
His relationship with Cesc is not like most between managers and players. Cesc knows he owes his career to Arsene. He's gone as far as saying he's as important to him as his own father is. He would not do that to him.
Besides. he's not even being sold, so the whole thing is a pointless charade.
He's calm mostly because he rarely reacts to anything, and because he's not being sold NOT because he thinks if he is sold he can get him. Well okay that might be incorrect, he might believe Cesc would choose Arsenal if he left Barca.... because Wenger's a little stupid these days. Cesc wouldn't come back to Arsenal the way they currently are to win nothing... again. He's no different to RVP, its not disloyal to join a previous competitor, its sport, its a job.
he's Barca's second best player, has played as if he's their second best player for two years, Barca has no reason to sell and Cesc has no reason to want to leave... thats the end of it really. Even if Utd made a 60mil off Barca felt they couldn't financially refuse, unless they tell Cesc to GTFO, he would still turn down a move.
Its quite funny, the press have been saying Cesc has been playing poorly for two years, isn't first choice and Tito doesn't favour him so he might want a move, even though Tito and Cesc both said categorically he isn't for sale and doesn't want to move. Tito leaves... who supposedly doesn't really like Cesc and the papers interpret this as.... his chance of leaving has increased, sure.
IF it were actually a situation where the player was disliked by the manager and the manager left people would usually say there was less chance of the player leaving, but the press want to push a made up story about Cesc leaving so logic has no part in it.