Excellent question. It depends on the size of your mining farm from hobbyist to professional. The hobbyist are less efficient and become less profitable first, ETH was started to appeal to the hobbyist miners. The professionals have a longer term outlook and will mine for a period of time at a loss if there is continued progress in the community for the coin they are mining.
The question though about GPU miner profitability vs ASIC is difficult to answer without knowing the number of ASICs on the network. Most of us that have large operations feel the numbers could be as high as 30% of the hash rate are ASICs. If we are correct Ethereum should want to protect the GPU miners at 70% of the hash versus the minority at 30% of the hash. The GPU miners are at a tipping point and once they leave the project, ASIC miners will be impossible to get rid of as their economies of scale will never let GPUs back in at a profitable rate.