I used to think that there's no way a 4K card would be called a GTX 1080, which is probably true. But the false assumption I think I made was that these are "4K" cards. If they change the name from the usual naming scheme, that would strongly imply that these are in fact 4K cards, but that's probably not the case.
This would explain why the leaked shrouds have the GTX 1080/1070 nomenclature etched on them. They might not want to give a false impression that these are designed for any particular resolution, 4K to be specific. So in that light, keeping with the usual scheme makes sense, particularly given a product stack that includes 1070, 1060, and mid-range, definitely not 4K cards.
What I don't like is repeating names. I think GTX 1080 is available, but AMDs upcoming 400 series reminds me of the Fermi generation from Nvidia. I've already been there, done that with a (GTX) 480, and had way too many discussions about a 460 vs a 470, and so on.