As noted on other threads, the GTX345R *will* work with G1000 GDU 12 software (the last version released for the DA40), but only the GTX345R version with built-in WAAS (for $800 more) and with its own GPS antenna connection.
Just for fun I stopped by the Avidyne booth at Oshkosh again this year for my regular annual question about when the "A" version upgrades to the TAS600-series with ADS-B IN traffic would be available.
The guy I talked to actually laughed (because it's been promised for so many years). He said the A version hardware is now complete, but that it would probably be "end of 2016" before the ADS-B IN software would be finished.
I told him Avidyne probably missed the "window" for market demand, since the Garmin 345R transponder with dual-mode (1090ES and UAT) traffic and weather ADS-B IN would be preferable to upgrading the TAS600 with only single-mode 1090ES traffic ADS-B IN (it will have to rely on ground stations to indirectly relay UAT traffic info, and no weather).
I fully expect to visit the Avidyne booth again next year to ask the same question.