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Degradation
Remember, if hash rate declines (no sign that it will so far), the net-effect is longer clearance times for large transactions.
It's not "failure" or "breaking"
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Certainly, if demand for blockspace isn't high enough to support clearance then the first thing to do would be to improve the utility of the chain so that demand for blockspace is high.
This is one of the strong reasons to support research like covenants and rgb and taro. If those tools become popular, we will see rising fees. Indeed, large miners should be *paying* researchers to advance these tools. It's in their own best interests.
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and on the other side I put game theory and well defined Prisoner's Dilemma.
The prisoner's dilemma does not state that zero stakeholders will mine, just far fewer. Real world experiments with actual prisoners and students show cooperation rates of 33%. Plus there are incentives. Stakeholders who want to move large amounts in a reasonable amount of time are incentivised to mine.
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Changing issuance is a non-starter, forte very game-theoretic reasons you refer to
it would destroy the value proposition of the chain, fork the coin and i have every confidence that the surviving fork would be the one without the new issuance