You wish!
You seem to think hardware prices will remain steady, in reality they will drop as fast as difficulty shoots up. Cointerra preorders are already being discounted at a rate of 50% per month now, not surprisingly perfectly in tune with D doubling per month, and thats not going to stop until marginal production cost approaches mining profitability per TH.
The latter is easy to calculate (I went with cointerra's specs), but the question is, how much does it cost to make more 28nm asics ? I did the math in another thread given a $5000 price tag per 28nm wafer (generous) and 2-3x cost for stuff like testing, packaging, PCBs and vendor markup, and it results in a difficulty somewhere between 100 and 200 billion at todays BTC exchange rate and with EU electricity prices. Thats a ballpark figure, it may end up being half that or double that, but not 1/15th of that, no way.
I cant predict how fast we will reach those levels, it could be many years, but the only thing limiting that is the ability of all asic vendors combined to produce and ship their products. There is no other limit. Considering the amount of vendors and the fact that at least some of them will be able to manage a supply chain better than BFL, I wouldnt be too surprised to see this happen in less than two years.
The reason Cointerra are dropping their price like a stone is they have yet to raise enough capital to fund NRE and they are expected to tape out imminently. You have to pay for your NRE upfront to receive your tape out results.
Cointerra are stick between a rock, and a hard place, they are late to the party and this is their last ditch attempt to secure NRE costs for their 28nm ambition. They don't care what price they sell their chips at as much as just selling the damn things to cover NRE so they can produce more wafers and make less profit over a longer timeframe.
I do rate Cointerra for being honest about their delivery dates though, Hashfast are just outright lying. Neither company will produce the anticipated hashrates and power expectations they claim per chip though. Those are just simulated best case scenarios, and they will not reflect reality. That's not me taking a swipe, that's me being a realist, unless they are performing some ASIC voodoo. 28nm is 28nm, you can create 2TH chips if you want, the issue is powering and cooling the chip.