Correct, right now it's only Windows/Mac/Linux. That leaves the whole mobile & console platforms without it, so it's not like our IL2CPP stuff is "not needed anymore".
So I guess CoreCLR will cause more work for Unity engine teams in the interim.
IL2CPP is great right now and gets past all AOT issues as the initial pain is over. Ralph Hauwert and those guys did a good job. It also gets compilation AOT down to C++ so it cannot be messed with by Apple. But I guess CoreCLR will be another standard/lib to manage and suddenly the standard xkcd on standards becomes relevant [1].
I can still dream of Unity Plan B from 2010 though with a fully C++ API that mimics the C# one.