The trustee report assumes benefits will stop being paid when the trust fund runs out of money and cost will either be made to conform or services rationed appropriately. The CBO just draws a trend line on health care costs and assumes they go up forever and we'll always pay them. I think it's somewhat possible that the US will look more like the rest of the world in terms of costs as time passes. It's also very possible that we may end up paying radically more for senior care than we do now in 70 years but that's something democracies continue to decide for themselves. There's no blank check being written today about health care in 2083.