As a hardcore SC2 player, I'd only be interested in a native version of this game. Even the latest ASM.JS demos like Epic Citadel run chopping on my system. Hardcore gamers like myself won't sacrifice performance for a the luxury using poorly designed and immature technology like JS and WebGL.
And Epic's demo was their previous gen engine, Unreal Engine 3, which targets mobile platforms: iOS, Android, PSP...
Meanwhile, the state of the art UE4 is only aimed at next gen consoles and native PCs games.