Not if your fpga small scale rig need to compete with AMD costs, who manufactures millions of GPU's a year.
We'll see. AMD devices do a lot more than just bitcoin hashing, and also FPGAs are manufactured in large quantity as well.
But you may turn out to be right. Time will tell. I'm definitely grateful that this open source contribution is being made, even if FPGAs turn out not to be the way to go for bitcoin.