@P_enta was close to being on the right track. The main reason why it can’t work on OS X/Linux is because of the DirectX API that windows uses. What it is, essentially, is the software that coordinates your hardware components to do useful things, in particular render/run 3D graphics. OS X is based off of a different ground-up way of coding that doesn’t really allow this to work without an overcomplicated way of adapting it to work, like a virtual machine or an emulator. The systems that allow Beamng to run simply don’t exist on OS X/Linux/PS 4 à la carte, and the devs are terribly interested in OS-level coding to get their game to run on a relatively niche platform. Xboxs work with an old, deprecated version of DirectX that could, potentially, with a metric ton of effort, run an adapted Beam. It’s far too much work to make the game run on worse hardware, so it’s not planned.
Oh yeah, why admins didn't prohibit CREATING that sort of threads? BeamNG will be Windows only. Full stop.
Controllers are a non-issue. You can easily fit what you need on a gamepad/racing wheel as is, and it would be even easier with some simple improvements. At this point I'd say there's a good chance we will see Linux support someday. As for distant future platform additions, it's only speculation for now. Obviously there is demand for it, so if recources allow for it then it would be silly to not give something to that customer base.