> Not 100% of users will accept the new software so after this event called "The Merge" there will be 2 competing Ethereum networks (actually 3 because there's already "ethereum classic" from the last time Ethereum forked).It's not actually that simple. After the merge, non-upgraded PoW nodes will automatically wind down and self-destruct according to the built-in difficulty bomb curve which is part of PoW.
For PoW Ethereum to continue running in a useful way to whoever wants to use it, a majority of PoW users would need to upgrade to a new PoW fork that changes the difficulty bomb curve. They have to coordinate and agree that fork, as different bomb curves are incompatible.
That would require a majority of PoW users to perform a coordinated softare upgrade, agreed with each other. There's no default PoW Ethereum that can keep working for a long time if people don't deliberately agree on and roll out a new fork.
> Bitcoin is very different.
Bitcoin has a difficulty bomb too (when coin issuing stops), so Bitcoin may eventually self-destruct too, if nobody steps up to coordinate a new fork of Bitcoin and a majority of users accept the new fork.
