Here's the answer from Garmin in the states about ADS-B IN:
The GTX 330ES supports ADS-B Out capabilities. In order to support ADS-B In capabilities a 1090 MHz receiver would need to be added to the transponder. This would be a major change and would involve a new product development effort. Garmin has no plans to add a 1090-receive capability to the 330ES. It is possible to add a separate receiver box that would support ADS-B In functions. We do not have a development under way to add the 1090 receive capability at this time. We are closely monitoring the proposed ADS-B mandate in the States and the Lower Airspace Program in Australia, and will make a decision on future ADS-B product offerings when the final decisions are made.
The GNS 530 will display traffic and will support ADS-B In display of traffic information. No future modifications should be required of the GNS 530 to support the display of ADS-B traffic. In the unlikely event that mods are required they would involve a field upgradeable software revision.