Makes me wonder who they could add. We already accept officers, enlisted, anyone who's honorably served, and their immediate family members (spouses, children, and down, but not sideways [siblings] or up [parents, grandparents]). I've heard people throw the idea of first responders gaining eligibility, but that doesn't fit with the spirit of military-only.
The only other group I can think of would be extended family like siblings of service members, parents, grandparents, perhaps cousins? Just taking a shot in the dark, I don't have any inside information.
There are regulators in certain states that don't like that we are military only, but USAA has sort of been grandfathered in. I think if we deviated too far from that and included first responders like EMTs, police officers, and firefighters, it might end us up in hot water with regulators. If we expand to extended family of service members, eventually we'll have "members" whose second cousin twice removed's sister's husband was in the military and feels entitled to the same level of service we give to a full bird colonel.
I don't pretend to know the ins and outs of this decision, that's just where my mind goes with it.