Title says it all: I would like to tell my users what version of OS X my project will run on, but I personally only have the latest version of OS X to try it on. Is there a standard set of OS X versions that UE4 supports?
Your game requirements would be the same as editor’s, see here Supported Graphics Drivers on Linux | Unreal Engine Documentation
In 4.11 we will be increasing the requirements, so please keep that in mind if you’re planning to upgrade. The minimum OS X version required for 4.11 and games made with it will be 10.10.5
A couple of things - it’s highly recommended for users to be on the latest point release of their OS X (10.9.5, 10.10.5, 10.11.3 as of the time I write this), to make sure they get newest graphics drivers available for their version of OS X. Also, especially on Intel GPUs, the performance on 10.10.5 should be much better than on 10.9.5, as on 10.9.5 we have to use some expensive workarounds for driver bugs…
Perfect! That’s exactly the information I was looking for, and thank you for the forward-looking information as well!