I can't see how you could possibly create an FPGA from a GPU, whereas you could/can create a GPU from an FPGA, for example Altera have OpenCL running on FPGAs, and also people have implemented GPUs using an FPGA.
Note that Altera's compiler for Open CL does not let you run your OpenCl stuff faster. It is intended so you can write your FPGA programs (that run outside of your computer usually) in OpenCL. Most of the imagined benefits kind of vanish, at least to me, when you realize that this is just a tool so if all you can hire if OpenCL developers, you can still get the job done.
