There are only gold miners in the original whitepaper. At the time of writing, nodes were supposed to be miners that used their CPU[sic!] power. Presently, the hard part has been outsourced to dedicated facilities (ASIC farms). But, and that's the point, these facilities are still controlled by a node (the pool operator), which decides on the blocks to work on and subsequently has petahashes of voting power.

Changing the PoW algorithm (your example) would require these powernodes to vote for their own abolishment, if their $100M worth of ASICs can't support the change. So it's very unlikely.