More importantly, there will never be more than 21 Million Bitcoin. That is the primary value it serves (beyond censorship resistance) it is not inflationary...
any scaling solution or consensus change that doesn't retain this important feature wouldn't be bitcoin, just another fork. potentially could go from PoW as long as supply is not inflatable it could still be considered Bitcoin (depending on whether users switched to the new version or not)
In case there's ambiguity here, I think GP means "core to the ideals" of Bitcoin, not the core of its implementation.
GP is correct. The Bitcoin community is fiercely conservative, and a proposal to switch from PoW to PoS would be met with about as much scorn as a proposal to increase the total supply.
Ethereum, on the other hand, has never had any strong attachment to PoW -- quite the opposite, really. Switching to PoS has been a major goal since the early days of the project.
any scaling solution or consensus change that doesn't retain this important feature wouldn't be bitcoin, just another fork. potentially could go from PoW as long as supply is not inflatable it could still be considered Bitcoin (depending on whether users switched to the new version or not)