What you call ROI is more correctly called operating income - which supports your point just fine. Return on investment is all about return on capital invested.
While ROI is calculated against capital investment, it does not assume the liquidation of capital. Now you could, of course, depreciate your capital, but that becomes rather insignificant with ROI in the mid triple digits.
That calculator does not take into account future difficulty. In a month, you could be only getting a third the bitcoins you are now. Make sure you factor in difficulty. As a general rule of thumb, the bitcoins you make in the first 10 days are 1/3 of all the bitcoins you are ever going to make.
While this is true, the question was weather we had reached parity NOW, and we have not. I don't see any way for the mining market to rationalize significantly expanding given the current legal and market uncertainty unless there is > 300% ROI on the day the hardware is ordered.