Too Long; Didn't Read
Bitcoin will most likely continue to use PoW although it costs a huge amount of energy. After ETH switches to PoS, the remaining tokens will have a much smaller market cap and energy cost. Within PoW, ASICs vs ASIC-resistant algorithms fare differently. GPU mining is beneficial toward global GPU producers. Once ETH switches to PoS, current ASICs, GPUs, and GMPs for ETH will have to find a place to continue mining or turn to a secondhand market.