The FAA recently released a legal opinion about exemptions from the ADS-B OUT mandate which comes into effect on 1 Jan 2020. The letter clarifies that all aircraft that were originally produced under a TC that did not require an electrical system would be exempt, regardless of whether a battery was later added. See the attached letter. Of course, to operate in Class B or C (or in D) would require special permission for each instance. As more aircraft are equipped with ADS-B OUT we might enjoy the delusion of great situational awareness by maintaining constant watch of our ADS-B IN display... but 'taint so. FWIW, NTSB midair accident data for the last 20 years show about 1 accident per year in the traffic pattern of non-towered airports where at least one of the involved aircraft was a FW powered NORDO machine. A couple of additional accidents involving NORDO aircraft occurred in cruise flight. It looks like See and Avoid is still the first line of defence, and will remain so for a long time.