If the membership shrunk down to the SIG level [of just a few thousand] the AMA could still exist at some level. There will always be some form of organized model aviation.
No amount of procelytizing will change anything, the future of the sport is in the minds and imaginations of future generations. As time goes by, the uniqueness and novelty of the sport has faded somewhat. Bigger and better ways to spend our free time keep popping up, model aviation will continue to get pushed further and further back into the shadows, but I could not care less. This is a great time to be in the sport.