A few more things have to occur before all of this becomes reality, though. The quick charging standard will have to be declared; some will argue that a dual-cable charging unit would be sufficient, but have you looked at the price of an 80A vehicle coupler lately? And the high currents from the supercharger require even thicker conductors, so having 3 cables per stall for CCS, CHAdeMO, and Tesla is simply going to be a non-starter from a cost perspective. The companies who commercialize this will want uniform standards. Perhaps we'll see a company start with the Tesla connector, then offer an adapter for the crazy monstrosities that are CCS or CHAdeMO (adapters work better when it's a smaller connector fitting into a larger connector).
So, then you have to attack the charging current problem -- most manufacturers are happy with a 50 kW rate (although I don't know why), but those of us who are used to over double that will be frustrated with the wait times on the road trips; supercharging is already "slow" to some. Yet when a Bolt or 200-mile Leaf plugs in and can only draw 50 kW, hogging the stall for 2-3x the amount of time that a Tesla will for the same mileage, it's going to make customers unhappy. So the upstart would have to either segment the population into multiple "lanes" of charging based on speed/type, or insist upon a minimum charge rate.
I'm sure there's a contingency plan for adding metering, billing, and payment to Superchargers, but my theory is that they won't be doing that unless compelled to serve third-party cars by government mandate. I definitely think a complementary entrant would indeed do that, along with various models -- subscription, fleet bill, and point-of-sale. Tesla's free model for Tesla's cars will help keep competition pricing from going out of control.
