Honestly, the adult Thrall speculation feels like the second Warcraft movie would have been, given how the last part of the first movie was basically sequel-bait leaning towards an adaptation of Lord of the Clans. I'm skeptical of them going for a Scourge/Arthas theme, given how heavily the first movie's success was carried by China. Would basically have to make a second movie just to remove the inevitable abundance of skellymen to appease China's censors.