4x22 The Enlightenment Launch

Theory
The season finale (episode 23 of season 4, otherwise known as "We are the Flash") is coming soon. But first we still have to get the episode before the finale (episode 22 of season 4, otherwise known as "Think Fast"). This episode will most likely have some build-up for the finale.

Launch
I think that in episode 22 of season 4, otherwise known as "Think Fast", they will let Clifford DeVoe, otherwise known as the Thinker, launch the Enlightenment device. This will most likely be the cliffhanger for the finale.

Verdict
In the end of episode 22 of season 4, otherwise known as "Think Fast", DeVoe was able to launch his Enlightenment device on the world. Which hereby confirms my theory.