I suspect that Bush may be released when JWill is ready to roll, and Lynn will use the duo of Gillislee and Williams to compliment Shady. There is no reason for Bush to be on this roster, IMO.
To respond to the OP, I think it will be interesting to watch the offense evolve under Lynn. Seems like folks here are writing him off already because he has never been an OC or called plays before. I don't necessarily think he is under qualified, as he has been an offensive coach in this league for a long time and has worked under some great offensive minds. Let's see the product on the field before we dismiss him. After all, the guy was respected enough around the league to get some HC interviews.