Paul Ryan's plan for Medicare and Paul Ryan's plan for Medicaid rely on the same bait-and-switch: They use a reform to disguise a cut.
In Medicare's case, the reform is privatization. The current Medicare program would be dissolved and the next generation of seniors would choose from Medicare-certified private plans on an exchange. But that wouldn't save money. In fact, it would cost money. As the Congressional Budget Office has said (pdf), since Medicare is cheaper than private insurance, beneficiaries will see "higher premiums in the private market for a package of benefits similar to that currently provided by Medicare."