Bit of theorycraft to consider. We've established that at least the next two Amiibo waves will be pairs: Joker and Hero, Banjo and Terry. Looking at Smash 4, if there's a significant gap between characters then they are typically released by themselves. Mewtwo was released by himself in October 2015. Lucas in December 2015. Roy and Ryu in April 2016. Cloud, Corrin, and Bayo in July 2017.
https://amiibo.life/releases
What can we take from this? Because of the significant gap between Byleth and Min-Min, Byleth will probably be released alone. This in mind, this is what we're potentially looking at:
Joker and Hero- September 2020
Banjo and Terry - November 2020
Male and female Byleth- January/February 2021
Min Min and 7- April 2021
8 and 9- June/July 2021
10 and 11 - September/October 2021
Based on this, the character announced in the fall Direct will possibly correlate with Byleth. Guess we'll see how things play out.