4x18 Elongated Man Death

Theory
In episode 16 and 17 of season 4, otherwise known as "Run Iris, Run" and "Null and Annoyed", Ralph Dibney, otherwise known as the Elongated Man, got portayed a lot. They added a lot of story around him and this got me theorising again. This is because most of the time when a character gets a lot of build-up something happens to them.

Death
Since Ralph is getting a lot of extra emotional value it seems that they're probably going to kill him off in the upcoming episode. This is what happens a lot to characters who get a lot of build-up. This would most likely be by Clifford DeVoe, otherwise known as The Thinker, taking his body and absorb his powers. In the trailer for the episode we saw DeVoe attacking S.T.A.R. Labs, this would most likely be to take the rest of the bus metas including Ralph.

Verdict
Ralph was indeed taken over by Clifford DeVoe in episode 18 of season 4, otherwise known as "Lose Yourself". Which hereby confirms my theory.