4x23 Elongated Man Goodbye

Theory
In the trailer for episode 23 of season 4, otherwise known as "We Are The Flash", we can see that Barry decides to enter Clifford DeVoe's, otherwise known as The Thinker, mind. Through previous spoilers we also found out that Hartley Sawyer, the actor who plays Ralph Dibney, otherwise known as the Elongated Man, was also appearing in this episode. This got people thinking that Ralph is going to be saved or brought back in the finale but I think it could be otherwise.

Goodbye
Since Ralph died when DeVoe took his body and his powers, it's logical to assume that he won't be returning. Also since Barry Allen, otherwise known as The Flash, is going into DeVoe's mind, I think that that's where Barry will find Ralph again. I think that Ralph, together with everyone who's brain has been fried by DeVoe are trapped inside DeVoe's mind. If this is true then they will probably do a scene where Barry says his final goodbyes and finally gets over his trauma just before Barry defeats DeVoe.

Verdict
In episode 23 of season 4, otherwise known as "We are the Flash", Ralp actually came back to life after Barry encountered him in DeVoe's mind. Which hereby debunks my theory.