I personally do not believe much in PoS as it has already been said here what is the value behind that,I don't see any real value and you need a large amount of ETH to be staked in order to have a saying how the coin will develop further.I will just keep mining the hell out of Eth and if it ever goes PoS there is RVN,ERGO and ETC as the next best thing to mine so GPU mining can be considered far from dead.
What will the other 2/3 video cards do?
You have to be very careful here, people don't like to hear the truth.