ADS-B will become a mandatory requirement in order to operate in certain airspace on January 1, 2020. The following is directly from the FAA FAQ ADS-B website and we hope it will provide some useful information regarding this upcoming rule.
On January 1, 2020, when operating in the airspace designated in 14 CFR § 91.225 you must be equipped with ADS-B Out avionics that meet the performance requirements of 14 CFR §91.227. Aircraft not complying with the requirements may be denied access to this airspace.

Under the rule, ADS-B Out performance will be required to operate in:

1. Class A, B, and C.
2. Class E airspace within the 48 contiguous states and the District of Columbia at and above 10,000 feet MSL, excluding the airspace at and below 2,500 feet above the surface.
3. Class E airspace at and above 3,000 feet MSL over the Gulf of Mexico from the coastline of the United States out to 12 nautical miles.
4. Around those airports identified in 14 CFR part 91, Appendix D.

The ADS-B Out rule does not apply in the airspace defined in items 1 and 2 above for any aircraft that was not originally certificated with an electrical system or that has not subsequently been certified with such a system installed, including balloons and gliders.

There are several transponders that meet the rule requirement, but you will also need a certified GPS position source or for experimental aircraft a source that meets the certification requirements but does not have to be certified.

Please contact us for additional information for your specific aircraft equipment needs.