As you indicate, the renaming may be a net loss for those who have to do he renaming, but, from Apple's viewpoint, is more than offset by the expected gains when writing new code by both current developers (where the gain may be small, zero, or even negative because they already are familiar with the API) and developers yet to start using Swift.

So, the question should be whether Apple should have prioritized new users of the language over their existing language users. I think they made the right call, more so because they pre-announced it. Not only didn't they claim the language was frozen, the specifically said it would see changes.