Absolutely true. This has been discussed many times on this forum. ETH comprises 95% of the block reward income available to GPU rigs. After PoS, the revenue we get will be just 5% of what it used to be at first, until network hashrate collapses to a reasonable level. At that point, GPUs will become very cheap, then revenue will recover, so it will make sense to build a rig again. But the payback time would be 600+ days.
The losers will be those who bought video cards at inflated prices but haven't reaped inflated 2021 profits.
Is going to be worse than that but you gave a good possible outcome of it, if people dont sell their mined coins now, it will be a lot worse than that but maybe there will be a last bulltrap before the merge and then will crash to hehell because all blocked eth coins that were staked will be freed and able to be sold in the market, too many eth coins were staked, the sell off after the merge will be insane and that is when we will know the true bottom for btc and eth.