Ever since the first Bitcoin crash there has been an anxiousness regarding GPU mining, this is largely because of how Bitcoin seemingly became unprofitable to mine overnight. But how did Bitcoin mining really become obsolete for most casual miners, and how can we predict whenever the same fate will befall Ethereum?
First, we need to look at one of the primarly reasons Bitcoin became unprofitable to mine. Partly the halving of the Bitcoin price played its part by making the rewards of BTC becoming more unobtainable for the casual miner. Lots of psychological factors also played in, as rumors of the unprofitabilliy began to spread and insecurity for the future of BTC stated to affect the price in a negative downward spiral.
But perhaps it was the success of the ASIC miners that ultimately made the BTC unprofitable to mine, as these massive mining factories of computers specifically geared towards mining bitcoin crushed all competition from regular GPU miners with their efficiency. There was simply no way the GPU miners could effectively compete with a factory full of super computers running on super high hashrates 24/7.
Ethereum mining has lately appeared as the most viable option for miners - and most profitable. While its currently very profitable to mine ethereum, miners dread the day Ethereum 2.0 with its "proof-of-stake" options and perhaps make Ethereum less profitable to mine. Further, Ethereum ASIC miners might come in and affect the competition the same way they did with Bitcoin once the supply diminishes.
But all in all, will this development really change the general profitability of GPU mining? While Ethereum might become less profitable in the future, there will be other crytocurrencies that take its place. One of those currencies is Ravencoin, that uses the KAWPOW algorithm that will prevent ASIC mining in the future. It will be possible that more cryptocurrencies will use the same algorithm for the same purpose.
So regardless, you should probably not be worried about investing in a casual mining rig at home (see this link for Tips & Tricks to improve your casual Ethereum Mining set up).