James Dempsey is hosting a super helpful website to show you Xcode version ships which Swift version.
Here is a little reminder that you can open it from the terminal for all command-line enthusiasts.
No installation of Xcode is needed 😂
If you are interested in creating a custom shell command to display the Swift version of your installed Xcode, then look at Jesse Squires blog post.
Jesse also links to an older article on writing a custom shell command to switch between multiple Xcode installations quickly. Jesse's articles are excellent, and I highly recommend following him on Twitter if you haven't done it yet.