The Medical Center has always been there... even while it was an active Int'l Terminal. For awhile there were rumors that AA
would move there and expand their SFOschedule, thus letting UA
take over the entire North Terminal (those were pre-9/11 plans which have probably been abandoned now).
Also, the current USAir terminal is suppsoed to be demolished (note that it is currently blocking brand new Gates A1, A3
and A5 at the New Int'l Terminal). But those plans got put on indefinite hold. If that were to happen, I imagine USAir would need a home (perhaps at the Old Int'l Terminal).
More recently the Virgin USA team toured it and perhaps could use it if they select SFO
as a hub.
My theory: With Terminal One sinking into the landfill perhaps it will hastily become the new home for AS