Why does it say "You can continue to sideload e-books on your Kindle via USB cable" at the bottom? Isn't that contradictory?
Being able to generally copy books to your Kindle by USB will not be going away. Books on your Kindle will not be going away, other than the historical reasons why Amazon pulls ebooks from people's devices (but that's not changing at all here). If you have a collection of DRM-free ebooks you can continue to use those and side load those by USB.