The IQ4 Trichromatic, as I understand it, only has the features of the IQ3, net none of the newer IQ150 features, interface etc. (frame averaging, dual exposure). I don't know if the features from the XF like focus stacking work or not as that is more dependent on the XF camera. If I have this wrong, then I apologize in advance. The IQ4 has a much better relationship with tech camera lenses, both the older Schneiders and current Rodenstocks, where you may not need a LCC after every shot (due to the micro lenses on the sensor) and the IQ4 doesn't need a mandatory dark frame after each shot. (You have the ability to do one if you want but P1 has a built in dark frame for the IQ4 that works for me 99% of the time)
Net, to me the Trichromatic is a one off, and it's science is based on true color with a different filter array over the sensor.
For me, costing etc, and with modern software the IQ4 offers more. And based on P1's history, don't expect any backwards firmware updates to a IQ3 or any 100MP sensor.
Paul