If anybody actually wants to know the details, CharIN (the organization that establishes CCS regulations and standards) provides all their information publicly.
Position Papers & Regulation
The regulations are constantly being updated so look at "inductive charging" to gain perspective. Connector standards are also different for different geographies but CharIN is striving for harmonization, as shown in the linked information above. Thus far adapters have not been permitted because the electric utility members fear high amperage non-controlled connections. It is logical to expect some sort of permanent connector solutions similar to that deployed for China-market Model S and X. Probably something similar will happen for high-amperage CHAdeMO connectors, with present Tesla adapters amperage-limited as they are already. In theory something similar could happen for CCS but I doubt it. Despite being a member of the CHAdeMO association it took Tesla almost two years to get approval for the present adapter.
Despite the foregoing I still think it is quite likely that the present Tesla CHAdeMO adapter will soon be enabled for the Model 3. Even though it is limited it is vastly better than typical L2 connections or even a full 80Amp HPWC.