Until someone can convincingly explain how depressurization can be linked to the loss of the transponders... yes, there are two transponders in the T7, left and right, selectable via the transponder panel, it seems difficult to see how depressurization would lead to the transponders failing.
The external antennas are in different locations (though I can't find my reference to where exactly). Turning off the transponder isn't just a toggle or push-button, the switch is a rotary and you'd have to move it two positions to get it into the standby condition.