We’ve release Xcode 11.1 GM today - the details are here: Xcode 11.1 GM Image released
There didn’t seem to be any release of a 10.3.1, so I think we are all up to date with the latest Xcode versions now, and the 11.1 image has the Xcode 11 CLI tools installed, too.
I’m working on changing the default Ruby to 2.6 no for Xcode 11 and newer, and once that’s fixed I will look at adding more simulators.