@Background is Best Pony
Probably over a year. Including time it gets approved, and licensed. So the second wave would probably come at least half a year later, depending on how successful these are.
After all, the SSB amiibos weren’t all released at once.
We will probably get the other characters in themed waves. Next will probably be antagonists like The Dazzlings and Trixie alongside the most popular background characters like like Vinyl Scratch, Octavia and Derpy. The Shadowbolts and Sci-Twi will be released alongside each other, and we’ll probably get more background characters released in the same wave as each other as well.