Nope, TCAS has always been based on secondary surveillance (i.e. transponders). Before ADS-B, it was based on Mode S. Air traffic control has used primary radar and even more primitive methods (position/speed/bearing reports over radio) to maintain separation since long before transponders. The in-cockpit automated "traffic traffic" advisory and "climb climb" or "descend descend" resolution advisory come from TCAS, which relies on transponders.