I installed the second Beta of 10.11 and Xcode 6.3.2 has stopped running.
The error is:
In order to open "Xcode", you need to update to the latest version.
The version of Xcode installed on this Mac is not compatible with OS X El Capitan. You have "Xcode" 6.3.2. Download version 6.3.2 for free from the Mac App Store.
It runs if you open it via the Terminal.
Thanks to the poster at developer forum who had the information.