That together with the halving of block prices ... it is the end for GPU mining.
The MH/s/$ is about twenty times that of the best GPU's ...
There is no way a GPU could ever compete against this price/performance numbers.
FPGA hardware costs are more per Mhash/s than those for GPU hardware.
Some people get electricity at either a tremendously low rate (e.g., those near hydro generation might pay as little as $0.05 per kWh or less even) or there is no marginal cost for consumption (e.g., included in the lease of an apartment or other facility). For them, GPU is more profitable than FPGA due to the difference in price for the hardware.
Now BFL's ASIC changes the game though. The cost of the hardware per Mhash/s is so much lower than GPU (under the assumption that BFL can actually deliver these and at the prices they've listed for sale). Each $100 of BFL's ASIC produces as many hashes about at much as $1,000 worth of GPU hardware. Thus the skyrocketing difficulty from even a marginal amount of ASICs delivered will make GPU mining yields so trivially low as to not be worth the effort.
Adding capacity now with GPUs hits physical limits, ... removing excess heat and access to electric circuits with enough amps. Using FPGAs though allows a greater level of Ghash/s without hitting those heat and power problems for most. Those might continue to at least be worth left running once ASICs arrive, at least for a little while longer.
The one-two punch to knock out GPU mining would be volume ASIC shipments and the arrival of the block reward drop (to 25 BTC, expected in December).