He'll walk if the jury gives a single damn about the actual law and the evidence. The prosecution introduced more reasonable doubt than the defense did! In closing arguments, O'Mara held four minutes of silence to show the jury exactly how long Trayvon had between the time he ran and when the confrontation started. If he wanted to get away, he'd have been home. Instead he doubled back and attacked Zimmerman. The prosecution's rebuttal? "Trayvon didn't have four minutes to plan his attack. He had four minutes left on this earth." (Technically true that he did have four minutes left on this earth after he ran, but still does nothing to answer the question of how he chose to spend them.)
I'm concerned that the jury is tainted, or that they'll cave in to emotional crap about a beloved son (whose mother kicked him out of her house) being taken "too soon", especially when they feel like they can "compromise" and still convict him on something because "it's just not right" that an innocent baby-faced child is dead and Zimmerman walks. Remember, the jury isn't told and I don't think they're even allowed to ask about sentencing, so it's entirely possible that they'll convict on Manslaughter thinking it's going to be a couple of years in prison, only to find out on the evening news that he was sentenced to 30.