"Well the good news is that if they stop pension benefits for new hires or anyone with less than 10 years of tenure, then the pension liabilities will eventually decrease as pensioners die out. "

True. In about 30 years. Until then, you have to keep paying into a system that doesn't have any new members coming in and contributing to the cost. Which is why switching from a pension plan to a 401-k style plan actually ends up costing you more money over the short and medium term than sticking with the pension plan.