When the series first premiered, The Flash followed Barry Allen (Grant Gustin) as he awoke from a coma after being struck with lightning during the S.T.A.R. Labs particle accelerator explosion and learned he had gained the ability of superspeed. Season 1 of The Flash largely dealt with the appearance of other metahumans created during the particle accelerator explosion, ranging from villains to other heroes. One such metahuman turned out to be Ronnie Raymond (Robbie Amell), the fiancé of Caitlin Snow (Danielle Panabaker) who was thought to have died in the explosion.
Rather, Ronnie merged with Professor Martin Stein (Victor Garber) to become the fiery metahuman dubbed Firestorm. However, a singularity formed above Central City in the season 1 finale, and in the season 2 premiere Ronnie was killed while trying to help The Flash as Firestorm. Amell later returned to The Flash in season 2 as the Earth-2 version of Ronnie, who had become the villainous Deathstorm -- though the character was again killed. Now, with multiple Earths in the equation, as well as the timeline-altering Flashpoint event, Amell weighs in on whether Ronnie could return to The Flash once again.
In an interview with ComicBook, Amell was asked whether fans of The Flash -- and the rest of The CW's DC TV universe that includes Arrow, Legends of Tomorrow, and Supergirl -- would see his version of Firestorm again; he said, "I hope so!" Amell additionally elaborated on the nature of the DCTV universe:
Well the nice thing is when you're dead in that universe there is always another Earth, but I think that version [Earth-1] of Ronnie is dead because he sacrificed himself to save the city, but you know there is always Earth-3, Earth-4, Earth-5...
Of course, on season 3 of The Flash, Cisco Ramon (Carlos Valdes) and Caitlin searched through the infinite Earths of the multiverse for a new version of Harrison Wells (Tom Cavanagh) -- which explains the arrival of HR and his bumpy transition to Team Flash. Theoretically, they could do the same thing for Ronnie, or Ronnie could return in some other fashion -- perhaps from either Jay Garrick (John Wesley Shipp) or Kara Danvers' (Melissa Benoist) Earths.
That said, it remains to be seen whether the creative team behind The Flash has any plans to bring Ronnie back from the dead once more. After his death in season 2, the series introduced Jefferson "Jax" Jackson (Franz Drameh) who has become the other half of Firestorm to Professor Stein -- and both Drameh and Garber have since moved on from The Flash to co-star in Legends of Tomorrow. So, even if Ronnie were to return to The Flash, it may not be to take back the mantle of Firestorm, but it isn't out of the realm of possibility, either.
The ‘Invasion!’ crossover event begins Monday, November 28 with Supergirl @8pm on The CW, and continues with The Flash at the same time on Tuesday, Arrow on Wednesday, and Legends of Tomorrow on Thursday.