I don't doubt that Superchargers will become available for all EV's. However, either an (expensive) adapter would be required for North American EV owners, or Tesla would need to install CCS-1 plugs on all its North American Superchargers.
Because no other EV uses Supercharger protocols that allow Tesla to bill EV owners, Tesla would need to do something to collect Supercharging fees.
I would not want to plug our 50 kW max i3 into a Supercharger whose maximum charging power is much greater when faster charging EV's are waiting to charge.
Because of existing charging plug compatibility, I won't be surprised when European Superchargers become available by the end of 2021. In fact, a U.K. i3 owner has already reported success in charging his i3 using a Supercharger. Some feel that being able to do this now is a bug because Tesla was not able to assess a charging fee.
I won't be surprised if North American Superchargers won't allow all EV's to charge by the end of 2021 due to charging plug incompatibility.
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