i compiled a short list of what would happen if:
miners would be delivered end of September and the difficulty will continue to rise 25% every 11 days (re-target time)
In my opinion, this is the more pessimistic view... i'm guessing the difficulty increase will level off towards the end of the year.

The -Mining should have been mining hardware cost

EDIT: is there a site that shows how much the difficulty rose every 11 days and has a history?
EDIT2: this calculation is done @ 108$/BTC