Mongosh is now built on top of Node.js 20.5.1 and will be shipped with the same in the final package / bundle.
This means that all the features introduced in Node.js 20.x, are out of of the box supported in mongosh REPL and mongosh scripts.
Also what it implies is that the platform support for running Mongosh (2.x) has been affected by this change, carefully highlighted in the scope doc here - https://docs.google.com/document/d/1kVWobRtSAEJlLBxREa-nPCT7ATrbN0Vb2B3iiQXI310/edit#bookmark=id.1f7p0djhanln