Iguodala gets points in open court and half-court. Against intuition, I see his half court scoring maintained, while his open court scoring down due to less running by the team. Iguodala got a ton of points in the open floor. The Sixers intend to be a running team again, but if they go away from this (they won't be as desperate to force the action, and will be playing with a lead more often) then Iguodala's scoring in the open court goes down. Thad will also be a bigger open court contributor this year, now that he can dribble better.
From the admittedly small sample of 2 summer league games, I think Thad is not ready yet to be a major ball handler in the half court at SF. I am confident he will play smart enough to contribute at SF despite his unrefined handle- but I don't see his scoring to be much more than 12-13 ppg this year. If that is the case, he won't cut into Iguodala's scoring opportunities in half court.
As I said before, I don't see Brand directly decreasing Iguodala's half court chances that much. The team may have only gotten maybe 10 ppg from the PF position- but if Evans converted some of his easy chances that number would have been higher without effecting Iguodala. Brand will have the Ball in his hands more, but Sam Miller(less posting) and Green(replaced indirectly by Thad) will have less touches. Brand's touches should open up easy looks and drives for Iguodala, balancing itself out.
I guess this adds up to about 18ppg. Maybe a few less open court dunks because the Sixers will slow down the pace a bit when they are playing with a big lead. Last year they had to scrap for ever chance to run. I think Iguodala will appear to be a much more refined scorer in the half court, since his job will be much easier not having to score alongside Evans and Green.