I think it depends on how he loses (I am assuming he will lose). Obviously if he gets crushed it will be tough to come back, but if he takes Vitali deep and it looks as though conditioning was the difference he will have better chances (provided he can use it as motivation to improve his self-discipline)
Really? I don't think so. Arreola will get punished in the usual slow Klitschko manner until he gets caught and stopped. It wouldn't suprose me if Arreola balooned to a stupid weight and fades into insignificance for a while until he decides to make a foolish comeback.