FPGA's are chips, they're mostly orthogonal to CPU's. Sure there's some overlap in the margins, but the vast majority of FPGA's do things that CPU's can't do. There is some competition because an FPGA can do everything a CPU or GPU can, but the converse isn't true: there's lots of stuff that an FPGA can do that a CPU or GPU can't. To oversimplify, an FPGA could replace almost any digital chip anywhere.