We've already posted the full patch notes for Version 2.0.0 of Mario Tennis Aces, due out Sept. 19th, 2018. There's one element of the patch that's worth mentioning on its own, though.
The game is now compatible with the Nintendo Switch Online smartphone application. If the application is running on your device when you enter an online match, you will automatically receive a prompt on your smartphone asking if you would like to join a voice chat with your opponent. This will be applied to all online modes (Online Tournament in Tournament, the new Co-op Challenge, and Online Play in Free Play.
While I know people aren't thrilled about using the app, I'm honestly surprised Nintendo is letting players chat with strangers! I'm sure complaints will role in shortly thereafter, and Nintendo will shy away from doing this again.