[2019] Is Crucible of Storms releasing with 8.1.5 or after?

Correct.

Also, the current plan is for Crucible of Storms Normal/Heroic to open on April 16, 2019, and Mythic/Raid Finder to begin a week later on April 23.

Battle of Dazar’alor is still quite new – a majority of organized raiders are working their way through their initial preferred difficulty, with higher difficulties to follow for many, and the final Raid Finder wing of Battle of Dazar’alor just opened this week.

“So much death here, so much power.” --Xal’atath