The BSA is not ignorant of geocaching.
While I don't know if there will be a geocaching MB (takes some time to create a new MB, prehaps an extension of the current Orientering one will do), they have made use of geocaching:
Geocaching was a new event made available at the subcamps at the recent National Scout Jamboree, done in partnership with Magellian.
Geocaching is part of the new leadership training event for boy scout youth leaders called National Youth Leadership Training. In fact, some scout leaders were a little annoyed at that, as they are concerned of the cost of GPSr and their ability to obtain these for their courses.
Within the Venturing program (co-ed 14-21 program), many are doing geocaching events as part of Venturing events.
(yes, I'm a BSA member).