If he hadn't canceled his order he would have made a few bucks of profit, in case KnC will keep promises and really over deliver in terms of Hash power, let's say 450 GH/s.
The biggest flaw in his calculation is that he's a groupbuy customer - not an average customer. So it's kinda misleading when he runs around screaming "it's not profitable" when it really is for the average customer. Groupbuyers ALWAYS overpay.
And your few bucks, could possibly be in the thousands. Kinda hard to see the difficulty doubling every month... forever.
When I said a few bucks I was sarcastic both because I did't really mean few bucks but a few hundread and because, as you said, exponential diff increase can't last forever