I don't see anything wrong with a Trailsport model of the Passport, just as Toyota has the Adventure model for the RAV4 or the TRD model across a bunch of their platforms.
If Honda was smart (insert comments here), they would put a 2" Lift kit on the Passport, some big old off road tires and wheels, a 360 degree Camera and call it the Trailsport edition.
I'm not sure where another platform would fit(?) Certainly not between the Pilot & Passport. I can't see them coming out with a giant SUV (ala Expedition and Suburban), Is there room for a new vehicle between the CR-V and the Passport? Perhaps, but my GUESS is that if it is a new vehicel, it will be between the H-RV and the CR-V..
Time will tell...