Got a very apologetic and polite email from Trig today (I'm waiting on the TY91 too, and already have the TT22 transponder installed).
The TY91 was delayed by unanticipated certification problems initially, then in the first batch there were a small number of radios where they were not completely happy with the quality control so they delayed releasing it to market.
They are only just now shipping and trying to catch up with orders. I have heard good reports about the transponders and a friend of mine just flew in a warbird in the UK with what he said was an early version of the com, saying that it worked really well.