The CBO Director has new presentation up and available here. Note especially slides 7 through the end, with slides 10 and 11 giving the expected makeup of the 2020 budget. All of these are shown assuming the 2001 and 2003 tax cuts are extended and the AMT indexed, and then assuming this doesn't happen. This is well said, from his slide 13:
"The United States faces a fundamental disconnect between the services that people expect the government to provide, particularly in the form of benefits for older Americans, and the tax revenues that people are willing to send to the government to finance those services."