...The retirement? If you think the government won't renege on its obligations to service members in the next 20 years, I've got some ocean front property in Arizona I can sell you. The idea that more costs won't be transferred to the member and that you have any kind of stability an a defined benefit backed by the government is retarded....
The government hasn't reneged on its retirement obligations for its former employees at least in the past century, if not much longer. While benefits for future members might be reduced as they have with the blended retirement system the government is pretty secure ground when it comes to funding military and civil service retirements, unlike many state and local governments that do have serious financing issues when it comes to their pension obligations.
There could be some things that could be done like changing the way pensions are adjusted for inflation but that would be very difficult to pass for the military. Freezing inflation adjustments for the life of a pension is one of the worst case scenarios but again, very doubtful it would ever get past the bright idea stage.
The main point, the federal government isn't like an airline where it can or will give up its pension obligations at the drop of a hat, things will have to be pretty bad overall (semi-failed state, collapse of the dollar, etc.) in order for that to happen. We are nowhere near any of that and won't be for a long time.