While the military are running AVGAS aircraft the production of AVGAS is assured on national security grounds, the RAF have a fleet of about 120 AVGAS burning Grob 115's and the USAF have just ordered a fleet of aircraft from Cirrus.
So I don't see AVGAS supply problems anytime soon, the anti AVGAS people are unlikley to get very far with an AVGAS ban when the amount of lead put into the atmosphere is so small and they have the Pentigon or the MoD to contend with.