"Never"?
As the PoS did actually launch and is actually working, I'm not sure it's going to be "never".
They may be late like so many software projects, but they seem to be serious about the switch to proof of stake.
Well as I understand I it was clear from day one that Ethereum would switch "one day" to PoS so miners knew, from the start, what they were in for.
> ... that invalidates millions of dollars of investment in mining Etherum...
Well the GPUs will not be able to mine ETH anymore but the ETH already mined aren't lost: the PoW chain is going to merged inside the PoS one.
I take it this all decided by the "Ethereum foundation"?