The obvious market and proving ground for a working "smart gun" is law enforcement (gun always on person when on duty, purchase decisions are by public agencies, etc.)
So, when we see a couple of years of deployment of such a technology with major police forces, we can see if they work and are reliable.
Well, I would argue they are safe when used correctly. The same way a table saw is safe when used correctly, doesn't mean plenty of people aren't hurt by them. I would say it's more political than that. Gun owners don't seem to be the type of people that would be excited to strap a microcomputer onto their firearm to decide when it can be used.
So, when we see a couple of years of deployment of such a technology with major police forces, we can see if they work and are reliable.