I believe this is possible as we have the Xavier NX dev kits but want to use the TX2 NX SoM for a project we are working on. I think we did this before we started using our custom carrier board. As an aside, we’ve found that some functionality of the SOM may not be exposed on the dev carrier board.
It might work, but we didn’t do the verification for all peripherials, might be problem there, and it’s not in our suggestions, we will not support it.