Grant Gustin recently commented that he would be open to returning as the Flash for a sequel series. I would love to see that happen, and I think that a sequel on Max, with 10 to 13 episodes per season, could actually develop into one of the best ongoing superhero shows we could have. That said, it does feel quite soon to be talking about a sequel to Gustin's Arrowverse series, as The Flash only ended two years ago. On top of that, I'd rather have Gustin play a new version of the Flash in James Gunn's DC Universe.
