1-3
Cause Akina Fujiwara is happy seeing the reaction of Charmer fans against Raina. Why? Cause in Pixiv, she got messages from her fans about the Light Charmer, and she replied their messages nicely. Plus, she bookmarked (favoriting) a fanart of all 6 Charmers done by a member in Pixiv.
Knowing her Charmers getting more and more popular, she probably already designed the new cards for Charmers, but....
3-6
....but, it depends on Konami, when they want the new Charmer cards released. Maybe not to early or not too late. Or...
6-10
...or after we wait in a long time, the design of the new Charmers are just finished/Konami wants to make the Charmer fans waiting their new cards too long.... just like we just got Raina...
11 or more booster, still could be possible...
I vote 1-3, though.
(Just a random pick XD)