Ralph Dibney aka. the Elongated Man (Hartley Sawyer) will be upgraded to a series regular in The Flash season 5. The character joined the TV show in season 4 and gained his powers after he and a bus-full of people were exposed to dark matter created by Barry Allen's escape from the Speed Force. It also turned out Ralph and Barry share a history, as Barry was the one who got Ralph fired from the Central City police force after he tampered with evidence on a case.
Ralph being exposed to dark matter was no accident, either. The whole thing was orchestrated by season 4's big bad Clifford DeVoe (aka. The Thinker), as part of a larger scheme that would allow him to absorb the powers of every "bus-meta" that Barry created (Ralph included). He almost succeeded after seemingly killing Ralph and taking over his body - only for the Elongated Man to make a triumphant return in the season 4 finale and regain control of his physical form, destroying DeVoe in the process.
CBR has learned that Ralph's story will continue in The Flash season 5, now that Sawyer has been bumped up to series regular status. Joining him as a new series regular this season is Danielle Nicolet, who plays Central City district attorney Cecile Horton (and the mother of Barry and Iris West's newborn sister, Jenna Marie). That makes Ralph and Cecile the latest permanent additions to Team Flash on the show.
It's not clear yet what the future holds for Ralph on The Flash. The character spent much of season 4 being taught by Barry how to be more of a selfless do-gooder and had become just that by the season finale. That said, the show has yet to introduce Ralph's wife, Susan Dearbon, from the DC Comics universe to the Arrowverse. It's possible that season 5 will explore an investigative storyline that brings Susan into the fold and thus sets the stage for her romance with Ralph.
Barry, meanwhile, will once again serve as a mentor to an inexperienced superhero in The Flash season 5. This time, however, he will be passing on life lessons to his daughter, Nora Allen-West (Jessica Parker Kennedy). Nora finally revealed her true identity to Team Flash at the end of season 4, but indicated that she had made a huge mistake that could have timeline-shaking effects. It's a good thing Ralph is coming back then, since it sounds like Barry will need all the help he can get next season.
The Flash season 5 premieres on The CW later this year.