This is a rumor around ethereum, I think it's just a FOMO way. If they want to reduce, the value will be the same. For instance, you hold 100E and it costs $20,000 total. If they decided to decrease ethereum amount, then your account balance is still $20,000. But you have only 50ETH left. In brief, you don't lose or gain any money on this process
Hope this will help you