They actually can not release the "correct" mapping. It wouldn't make sense, games with Quick Time Events that ask you to press "A" on a 360 controller wouldn't magically visually change it to "B" Icon on screen to match the Wii U Pro, it would still say "A", and then you would have to remember to press "B" on the U Pro. Awkward. You would have to memorize the button layout because the letters won't match up if they flipped the mapping. But if you think about it, a 360 controller has X and A NEAR the right joystick, even though the Wii U Pro Controller is a different layout, X and A are also NEAR the right joystick. So it should be an easy switch.
Remember, Microsoft are the ones who changed the layout mapping, NOT Nintendo, they had this setup since the Super Nintendo. But I can understand if you are use to a 360 controller, muscle memory is hard to break. Its been a few years since I really got to use a 360 controller so the switch to the U Pro controller was super easy for me. Personally, I have been absolutely loving it!