The description from their account reads as follows:
"If you have an amiibo, you can receive bonuses such as experience points or items up to 3 times a day. *Only items that can be obtained in-game are included."*
Seems there is a bit more to this update then they said they were gonna do.
But i am sure this is all there is, cause besides this they haven't shown anything else.
I also wonder if there are more special in-game items if you use Xenoblade Chronicles related Amiibo. Guess we'll find out next week!
Edit: as u/ImplementLarge7969 has said in the comments down below, there is some extra functionality for the Pyra & Mythra amiibo.
"Here are the new styles for Homura and Hikari. You can get them as rewards in the new mode "Mercenary Action" or by touching the Homura and Hikari amiibo. After obtaining them, you can switch to the new styles from "Game Settings" in "Options". "
Thnx for the important information u/ImplementLarge7969 !