We're not in the predictions business, so I'm loathe to guess what Jan Brewer will do, but I think it's safe to say most people watching this closely will be stunned if she doesn't veto the bill.
The timing of this announcement suggests as much. We were expecting the announcement to come Thursday. Doing it today, relatively late in the day even by Arizona time, suggests that the damage to the state and her reputation were becoming too great to delay the decision any longer.
It's almost as if the NFL looking for a backup site for next year's Super Bowl was the final straw.