I think I would have stuck up for Rennie until the Italy game at that point he lost me. I put that loss on the selections and coaching decisions (substitutions). So, I agree he isn't the guy to lead Australia to any form of glory. I hope I'm horribly wrong....
I just don't think Rugby Australia will do anything at this point like Wales & seeming England so we are just bashing our heads against the wall. If it did happen to occur, I think they would just hand the clipboard and pool noodles to McKellar to have it be quick and as cheap as possible. I don't think anyone (Robertson, Sexton, Joseph & others) would come near Aus without a 5year contract put in front of them which I don't think Rugby Australia will do.
I think DC is probably the best coaching prospect not involved in the national set up. With Cron also shown to be able to produce results at levels he's been at like DC.