Which means DOUBLE THE PROFITABILITY!
This is simply not true. This would only be true if your MMQ used up 33% of its earnings in power usage, and the Single used up 66% of its earnings in power usage. In reality, these numbers are only 4.5%, and 9%. That is still technically half the operating costs, but it's not twice the profit.
I think he meant when difficulty catches up; ie, miners are back to operating at barely a profit.
Well he's always used this argument as a selling point of the MMQ, and I think it's misleading.
In fact it could be (in a theoretical stable Bitcoin world) misleading in the opposite way. Eventually, market pressure should bring mining profit to a relatively low margin above electricity costs. This doesn't work that way currently because the market is unstable (mining hardware evolves and BTC price too). But if you took 2 mining hardware solutions with a difference in efficiency higher than the low margin (I guess 20-30% should be a sign of a mature market), the low performing hardware wouldn't even be profitable.
It doesn't matter anyway, if ASICs show up this year, I'm not sure any FPGA will have paid for itself when the difficulty will put them out of business.