Don't really want to argue, but if you are on the major league roster you accrue service time. I don't think that would be a significant factor for the Twins, just one of many. I think it will be a case that he isn't deemed ready and they don't want to call him up to sit on the bench.
Just because the Twins are out of the race doesn't mean they are going to suddenly bench Willingham, Span and Revere. It doesn't work that way. And I would think Benson gets first crack at a September callup. Of course, and as I said, if there are enough trades and injuries it might open up a spot for Hicks, but a lot of things would have to happen for that to occur, not the least of which is he needs to keep up this pace for the next 2 months and not hit a cold streak as he has done in the past.