Pensions are not inherently unsustainable. They exist in the private sector in other countries and there are still some well funded private sector pensions in the U.S. They don't work well if they are not properly funded. Corporations got rid of pensions not because the concept is inherently unsustainable but because it's more profitable to do away with them.

My pension plan is not a good one. You characterization of one group of state employees giving a dream set of benefits to another is not based in reality. Administration does not negotiate strongly with us the contract won't be approved by the legislature or signed by the governor. Our wages relative to buying power has not been going up or remaining steady.

If pensions are inherently unsustainable then you must conclude that it is unsustainable for a society to care for itself.