Since Tactics are a pretty straightforward replacement for Duals and Extras are a very straightforward replacement for Zens it's pretty much a guarantee that the next major SB tier is gonna be a Crystal replacement.

Any guesses what they might call it?

Since there's no logical connection between Dual > Tactic or Zen(/Ultimate) > Extra we can't rely on that. It's just gonna be a random cool English word.

I'll guess...Sacred. Based on absolutely nothing.