When I was in Australia, I met David Brown, had long conversations with him and also watched him teach.
A general point: where you have organizations with a very strong vertical structure between the shihan and the rest of the organization, the shihan's passing will inevitably pose serious questions. Do you try to carry on as before, or do you acknowledge that an era has passed and search for another way? Some Aikikai shihans actually set out to create a corps of senior 'clones' quite actively (the SHU-HA-RI paradigm, with the direct link between master and student, can be a convenient tool for this). But others are less active and when they go, the organization can have severe problems.
Sugano Shihan always led from behind, but he led, just the same. His passing, however, will also affect the relationship between Aikikai recognized student-shihan relationships in Australia and the Hombu.
Just a quick follow up, there are several aikido organisations in Australia that are affiliated with Aikikai hombu and vary in their approaches to exclusivity. IMHO, and you seem to have a similar view, its about finding the right teacher too.
I've had some terrific practice with David Brown Sensei (Clifton Hill, Aikikai Australia) in the past as well as others in other organisation in melbourne (though am not a member of AA nor live in Melbourne)
best wishes in the search / decision