Just keep in mind FPGA will be dead once ASIC is released 500Ghash.
Doubtful. Firstly we all know BFL's track record. If they say ASIC release is 12-16 weeks off you can read that as early 2013. BFL is in business to make a profit, so regardless of what BS is posted now, the units will NOT be inexpensive.
Secondly, for FPGA mining to "turn off", the difficulty will have to be so great that it costs more to mine in electricity then btc you can generate. Spartan 6 based miners are very efficient (and next generation even more so).
Thirdly, even if that electricity/btc point is reached, you can repurpose your FPGA miner. Worst case scenario is you can sell off the board to a third party to salvage the FPGA.
Lots of people said FPGA will kill off GPUs and you can clearly see that market is still flourishing.