Over the years, Barry has clashed with both versions of Reverse-Flash in The Flash. Additionally, the Waverider crew battled a time remnant of Letscher’s Reverse-Flash in Legends of Tomorrow season 2.
In The Flash season 6, episode 15, appropriately titled “The Exorcism of Nash Wells”, Team Flash managed to “exorcise” Thawne from Nash’s mind. However, this does not mean that Thawne is dead.
This is cleared up during a conversation between Barry and Cisco at the end of The Flash episode. They both understand that even though Nash is free of Thawne, this may not be the last time they see the villain.
If Cisco’s theory in The Flash is correct, then it stands to reason that when Reverse-Flash returns, there will be one key difference: Reverse-Flash will be played by a third actor.
To revert to a corporeal form, Reverse-Flash may have to find someone weak enough to control in The Flash. The new host for Reverse-Flash could be anyone, even a female character.
Even though both actors’ performances have been met with much praise, casting someone else in the role can prevent The Flash’s Reverse-Flash stories in the Arrowverse from becoming stale and allow for a remake of the character.