( Ethereum can be the base layer of that too - and a very good one, as the common root of trust makes it far easier to move assets between rollups safely and cheaply.)
While there are many paths toward building a scalable and secure long-term blockchain ecosystem, it's looking like they are all building toward very similar futures. There's a high chance that block production will end up centralized: either the network effects within rollups or the network effects of cross-domain MEV push us in that direction in their own different ways. But what we can do is use protocol-level techniques such as committee validation, data availability sampling and bypass channels to "regulate" this market, ensuring that the winners cannot abuse their power.