That's cause FPGAs weren't really better. Their only point was lower power consumption, which was a big deal when BTC value was at the bottom and profit margins were small. Now that they've improved, FPGAs aren't that lucrative anymore. They were always more or as expensive as GPUs.

ASICs, on the other hand, improve over GPUs on all fronts. You get far more GH/s per BTC than you do with any other option, and power usage is greatly improved again. So yes, ASICs will kill bitcoin-mining GPUs definitely, but non-SHA256 cryptocurrencies will likely remain an option.