Well, I don't see why we would make it private.  It will end up user-facing because if you do ``pyplot.gca()`` or similar that's what object you will get.  So I think it should still be treated as a "public" class in terms of API decisions.  (Also, I could certainly imagine someone wanting to subclass it in some circumstances)

Don't get me wrong, I agree with you that `wcs` is a sensible place right now... I just don't think we want to treat it as "subordinate" to the current `WCS` given that we'd rather it eventually be tied more closely to the generalized WCS.  <shrug> (I wish there was an emoji :shrug:)