Why do you think we'll never see it compiling iPhone apps? Neither the technical reasons - i.e. garbage collection in the iPhone Objective-C runtime, not the political reasons - the infamous 3.1.1, I presume, it doesn't do so already seem to me insurmountable. Especially since it is an Apple run project and one of its main goals is to be a first class Obj-C equivalent.
It's important to remember that when NeXTStep and Objective-C were first invented, they were invented explicitly from the inspiration of Smalltalk. Apple today is a descendant of NeXT. I'd speculate that not only that they've taken notice of Ruby, but have decided that since Ruby is the spiritual descendant of Smalltalk, it's worth trying to make Ruby the first-class applications programming language for OS X platforms.