The Flash season 5 finale saw Cisco Ramon taking "the cure" that would forever remove his metahuman powers. This means that his career as the crimefighter Vibe has come to a close, but there's nothing in the episode to indicate that Cisco is abandoning his friends at STAR Labs, despite a rumor that actor Carlos Valdes was not returning for The Flash season 6.
It was previously reported that Valdes was leaving The Flash after season 5 to return to Broadway. However, the rumor was never officially confirmed by Valdes or anyone associated with the show. Valdes did poke fun at the rumor, however, during a Q&A at Fan Expo Vancouver in March, where he answered the question of whether or not he was leaving with a mouthful of food, rendering his answer unintelligible.
Cisco's arc over the course of season 5 saw the mechanical engineer develop a major change of heart when it came to his superheroic lifestyle. After nearly dying at the hands of the serial killer Cicada and faking his death as Vibe, Cisco began to become obsessed with the idea of creating a "cure" for metahuman powers that could allow anyone who wanted to lose their powers to do so. Eventually he realized that he wanted to give up being a superhero to focus on making a difference in the world with his inventions, rather than by fighting metahuman criminals.
"Legacy" saw Cisco finally make the decision to remove his own powers after an encounter with the Reverse-Flash, who said that he always knew Cisco had it in him to be extraordinary, making reference to his powers. With Caitlin Snow's help, Cisco administers the cure to himself. Saying that he is scared but hopeful, Cisco leaves the lab after telling Caitlin that he left something for her in his workshop - a new costume for her Killer Frost persona. When we last see Cisco in "Legacy," it's during a closing montage where we see Cisco with his new girlfriend.
While Cisco's days as Vibe may be over, there's nothing to indicate that he is never appearing on The Flash again after "Legacy." He didn't quit his job at STAR Labs or tell his friends that he was moving away from Central City. There's also no reason he'd have to choose between his girlfriend and his superheroics as "Legacy" also saw Cisco revealing his secret identity to her and she was more than understanding about his keeping his powers a secret. Indeed, she said that she didn't have any issue with him trying to balance their romantic life with his second life as a superhero.
It's possible that Carlos Valdes has been given a soft exit, similar to the one Jeremy Jordan received at the end of Supergirl season 3. Jordan, who played the role Winn Schott, wanted to take some time off to do a musical theater tour and his character was sent off into the future, with things being left open as to whether or not he might return later. While it hasn't been made explicitly clear that Cisco is abandoning every aspect of his life at STAR Labs, the possibility is there. It's also possible that Cisco will continue to provide technical support to Team Flash - he just won't be joining in the fights anymore. Whatever the case, The Flash will be all the poorer in season 6 should Valdes not be a part of the cast.