I think they should update the tokens and the “end of battle rewards” this way :
4* : After the first season where they’re set as reward. (or in the update following it)
3* : After each end of a new char first “Versus event”. (or in the update following it)
2* : After the event using them in the red essentials fights. (or in the update following it)
This is the first season where they’ve established a sort of “rotation” of characters. They pulled 5 or so characters out of rotation “for possible re-work” and intimated that they’d bring them back at the end of the season. So it’s pure supposition on my part that another set of characters will get rotated out and in.