Sodium is absolutely less of a fire risk which is good and is made of less rare earth minerals which is also a bonus. The major downside is the energy density. If I am not mistaken it is about half of current litium ion batteries. Which would result in a halving of range for the same weight. On top of that, if they ever get them into production, the solid state Lithium ion batteries are not only more energy dense than current batteries, they are also safer due to the lack of flammable liquid electrolites. In conclusion with what I know, I doubt most cars will use sodium ion batteries. I would see them as great home batteries for solar installations. And maybe batteries for farm equipement or construction vehicles although the weight might become an issue.