We’ve just discovered that iOS 11.3 beta 4 has reverted the iBooks to Apple Books. But that’s not the only thing change in this release.
New string files found in this release suggests that the TV app is likely arriving in Brazil soon, since the app has never supported Brazilian Portuguese before. This could coincide with the release of Apple Pay in the country, as announced by Tim Cook in the latest earnings call.
The TV app is currently supported in the United States, Australia, Canada, France, Germany, Norway, Sweden and the United Kingdom.