That blog has the lamest explanation about why x11 FPGA's don't exist yet. First he admits FPGA could be programed to to mine x11 since it is much less system memory intensive than scrypt, then he goes on to speculate the dramatic increase in x11 hashrate by single miners, which some pools have seen 1.2 - 1.8 GH/s from single miners, is due to GPU farms. How many GPU's do you need for that?
The low profitability of x11 coins even when compared to scypt coins with known ASIC miners confirmed suggests something more may be at play than is currently common knowledge and that fact x11 makes GPU's more energy efficient also suggests they are not ruining at their maximum potential with the current miners wildly available. There are also no facts that show x11 is any less ASIC resistant than scrypt was.
The price of FPGA's have come down substantially, especially in China. You can even buy boards for as little $99:
http://elinux.org/Parallella_Hardwarex11 FPGA farm deniers are starting to sound a lot like scypt ASIC deniers from as little as a few months ago. The fact is if something can be done at a profit, there is no reason to believe it won't be done, that is the nature of entrepreneurialism.