States can try to raise income taxes. And people will move. States can try to raise business taxes. And businesses will move. What can states tax that can't move? Only real estate. If the state drastically raises the property tax, there is no choice but to pay it. You can sell, but the new buyer will be willing to pay much less. Pay the tax slowly over time, or lose the value of the property right away in a lower price. Either way, the owner of the property on the day the tax is announced bears the burden of paying off the pensions.
Politicians will shrug their shoulders and say: "We had no choice, now that it's a crisis we knew about for decades."