It is possible on different OS's to find plug-in versions by viewing a bundle's properties sometimes, or by drilling within the .bundle package to find the properties of certain files therein. This can be a tedious and often fruitless process as different operating systems display properties in different ways and different places.
One consistent place to find the version of your plug-ins is in the Info.plist file. This is inside the plug-in bundle file. On Mac OS X you will need to show package contents to access this file. On Windows OS's you can simply open the .bundle folder. The Info.plist file is inside the Contents folder of the package. Open it with any text editor to find the necessary information.
The plug-in version is stored in the "CFBundleShortVersionString" key value. Below is an example from the release version of 4D v11 SQL Release 5 (11.5) 4D Pack plug-in: