Mining rigs have a finite lifespan & the places that make them in large enough quantities will stop making new ones if a more profitable product line, e.g. AI accelerators, becomes available. I'm sure making mining rigs will remain profitable for a while longer but the memory shortages are making it obvious that most production capacity is now going towards AI data centers & if that trend continues then hashing capacity will continue diminishing b/c the electricity cost & hardware replenishment will outpace mining rewards.

Bitcoin was always a dead end. It might survive for a while longer but its demise is inevitable.

Are you lumping in all blockchains here or just bitcoin?

Because other networks don't have this problem.