To me FPGA's = loser in the long run. Short term they can be good.
I know a lot about chasing mining gear since I have mined nonstop since 2012.
You can not make constant profit with mining gear unless you have a power angle = fact. In fact it is the basis of Pow coins turn power into coins.
I betcha some FPGAs that were in use to mine BTC back in the day are still mining (alts) today. The more algos there are out there, the more edge the FPGA's have... if you know how to (re-)program them. Which the majority of people out there does not.