I have been called a rollup shiller before, but I am bearish on this roll-up-centric roadmap and in favor of keeping the original plan of general-compute shards (ETH2 Phase 2), for a couple of reasons:
(1) validity proof of general computation are already here, see Cairo, Zinc and Noir by StarkWare, Matter Labs and Azteck respectively. So, it is not inconceivable that the runtime of shards in Phase 2 are provable in zk. Yes rollbacks of ORUs are localized to the offending contracts and not the network as a whole, but ORUs are a short-term solution anyway and may not even be universally viable because of capital efficiency vs security problem. So there seems to be a pre-mature optimization here.
(2) by reducing itself to merely data-availability and proof-enforcing layer, Ethereum risks losing its hard-earned network effects. These effects “grow” out of webs of interdependencies between L1 contracts … and by removing general compute, those webs start growing as inter-L2 dependencies. But then, rollup #1 having can keep its dependency on rollup #2 without necessarily being dependent on L1 for security. It just runs a light-client for ETH2.0 and outsource its own security to some other chain. This is different from when L2 rely heavily on logic on L1 to function. We should push to thicken the amount of logic on L1, not reduce it.
(3) if Ethereum takes over the world, there are many use cases that require nation-state-grade and enterprise-grade security and availability and may not tolerate the possibility of some withdraw delay due to an uncooperative ZKRU chain or a detected fraud in an ORU. Example: end-of-day inter-bank settlement logic … these people are gonna want to do this directly on L1.
(4) Having a proof-powered state- and data-shared ETH2.0 should improve scalability massively because the beacon chain is verifying proofs of proofs (whether fraud of validity) … so I don’t see why the scalability goes down (?). Unless Im missing something here.
TLDR: Rollback risks are not existential. Validity proofs of general compute are here and prover markets and ASICs will pop-up if necessary. Ethereum network effects are at risk if shards are not general-compute.