Whether you are collecting Social Security or not ... unless you are Medicare definition disabled ... you receive Medicare when you are sixty-five. Moreover, whether you are collecting your SS ... or putting it off until seventy ... You, if you have your forty quarters in ... will get Medicare ... even if you have creditable coverage. Whether you opt out of B, or not ... you have A. No penalty for delaying Part B, if you have creditable coverage.
In addition, it's only 80//20 on outpatient. Inpatient, facility based charges ... after the deductible are paid at 100%.