I think FPGAs are too expensive to be used for general purpose computing. If on top of the chip price you add the development time it's just not cost effective. A high-end FPGA will cost you thousands of dollars and you won't be able to easily convert software code to HDL. A very high end GPU will be cheaper and easier to develop for.

There are situations where a FPGA is better suited of course (very low latency real time signal processing for instance) but for general purpose computing FPGAs are not exactly ready for primetime IMO.