I think it is pretty naive to think that the laws won't be changed. Taxpayers aren't going to sit back and fund lavish pensions for govt workers when the taxpayers have seen their own retirements decimated.
I don't naively think that laws won't be changed. I think laws probably will be changed because they have to.
When a private company promise a pension to someone then renegs on it, that is illegal. But it is a civil issue. The retirees can sue the company. The company can declare bankruptcy. Then a bankruptcy judge can "adjust" the pension obligations. Usually though it doesn't come to that. There is a settlement.
In the case of a government pension though things are different. If the government tries to reneg on the pension, that would be a "taking" which is unconstitutional. The government can be forced to raise taxes to pay the pension obligations.
In spite of all the political jabber, a state cannot declare bankruptcy. If laws were changed to make that possible, it would simply mean that a bankruptcy judge raises taxes or auctions off the state's assets rather than the legislature.
For the Federal government, there are some other constitutional issues that would need to be overcome. Again, in spite of what the politicians say, it is not legal for Congress to put the country's debt in doubt. Any action by Congress to default would not be legal. And entitlement obligations would have to be paid before bond interest.
There is no doubt that we are in bad shape and some serious changes are needed. But there is an awful lot of fearmongering going on. When you look at the numbers you find that, in the case of the Federal obligations, it would take only a 2% tax increase to make it all better.