Rita was knocked into space during the climactic battle, but it’s unclear where the Green Power Coin ended up.
When Power Rangers images started being released, many fans suspected that the green jewel in the center of her staff was actually the Green Power Coin.
Sure enough, they were right, and in the movie’s prologue, Rita was seen betraying her Ranger teammates so she could take over the universe.
That said, since Tommy Oliver was name-dropped in the movie’s mid-credits scene, it’s only a matter of time before it makes into his (or her) hands and a new Green Ranger emerges.