Their incentive to stop is the same as Bitcoins. They're throwing money down the drain and don't have infinite money. You can argue they can't spam for as long on Bitcoin. In the same hypothetical situation Bitcoin fees would climb much faster and be much worse off and stay that way if it is sustained because it's blocksize doesnt adjust. Bcash has dynamic blocks now by the way.

Last part depends on rate of adoption, protocol improvements, and consumer tech advances. Just like we can easily run a Monero node at the current rate of adoption no problem. Bitcoin just gains easier validation at expense of higher transaction fees - which just centralizes in a different way (no one will run a node for a network they can't afford to use)

https://nostrcheck.me/media/af740d198babb8c7b82d0a4718eb354bb3f6af9a98639b85d4a5cf1371caba85/563fe6fae92d9f1459b7f4bc85978712a23a1b2c08bd389e681bad97f97a84e7.webp