Froggy, I think the TC55 with hydro is unlikely because of the size, pressures, and temperature required to operate with the higher power of the TC55.
The Class III tractors already run at 5000 psi maximum pressure. To keep pressures under control, you could increase the size of the hydraulic motor, but then you have to have a much larger physical space to put it into. You also have to keep it cool and that's no small problem to solve either.
I think the TC55 is larger than any of the JDs you mentioned. I'm not sure about JD, but the hydro transmission on the NH TC35DA has no less power output than the one on the TC40/45DAs. They all have the identical relief pressure, so the 40 and 45 just waste power a lot of the time.
I wish there was actually a hybrid transmission that could provide hydro like controls for low torque applications like mowing and other primary PTO functions. When doing draft work, that transmission would change to gear mode and be driven directly. As long as I'm dreaming, I figure I might as well dream big. /forums/images/graemlins/smile.gif