SERVER-23570 is fixed, Windows will exhibit a limit to the number of databases that can be created with on-disk encryption enabled. Today that limit is ~30, after the fix to SERVER-23570 it will be ~5000 (this is an estimate). But there is no reason for this to be a fixed limit at all, it could scale to whatever the environment is able to handle.
In Linux the same sort of limits will occur (in fact, the limits are lower by default), but they are adjustable at the operating system level using the instructions in DOCS-6885. There are no equivalent instructions for Windows.
Windows requires an API call; SetProcessWorkingSetSize and MongoDB could try this when it gets the error code indicating that locked limit has been reached.