What will happen after the transition of eth from Pow to Pos? According to my scenario this would mean the demise of ethereum. Because? well, let's start with the fact that pow is based on millions of mining rigs around the world validating blocks. These resell the earned and when they have paid off the machines and the electricity, they set aside a little ethereum to buy more performing machines or optimize consumption. With the pos these will become useless with the consequence that ethereum will also become useless for them. It will be a much more centralized cryptocurrency for the rich few. Just my opinion.
Edit1 The effect of the miners (and therefore of the economic empires of Nvidia and Amd which have an interest in increasing the values of some crypto to sell more cards) will be felt just as it was felt on the various litecoin then dash etc?
There's so many people willing to stake their coin and replace these miners. like it or not I think the miners are rather more centralized now as I see small individual mining just doesn't cut it and not profitable anymore. Also, with mining rigs you need to renew it every year to compete with other miners.
In my opinion there are many miners that willingly to sell their mining rigs and switch over to staking coin and one of many advantage is that they don't need to think about maintenance and other things.