Avgas will be with us for decades more.
I'm not so sure there. I'll readily agree that "fossil fuels" in general will be available for quite a while - longer than my lifetime, sure enough. But fossil fuels ARE on the way out, and AvGas being a rather rare variety it will be among the first to go. MoGas will stay a bit longer, especially if alcohol-doped; diesel/kerosene much longer, because a lot of commercial transport depends on it.
Energy density does not necessarily = danger
Oh yes, it does. The question is: to what degree is the danger known and addressed and controlled? Surely fossil liquid fuels have their own dangers, and accidents can and do happen, but the risks are known and there are procedures to deal with issues. With batteries, much of that knowledge still needs to be built up. For one example, fire brigades are recently learning that a car with a burning battery can only be extinguished by immersing it in a tub full of water, and such tubs are now being constructed here and there. How to deal with the same condition in your SEE is yet to be determined.