I don't see any stats saying VSCode has won "everything that isn't enterprise Java", that's clearly wrong as it's not really used for .NET stuff and most C++ for gaming is still classical Visual Studio. And JB IDEs have a lot of traction for any language they support outside of Java too.

GitHub Codespaces isn't a revenue model for the IDE. It is a separate product that requires a separate team, so it'd have to be charging a lot of money indeed and get a lot of users to fund two products for the price of one. It also looks like a rather basic featureset - if it takes off as a product it is not very hard to integrate into its competitors or build a similar system.