It got leaked(?) in chinese. Spoilers below cut:
Archimonde: Gul’dan, you signed pact with me!
Gul’dan: NO! *EXPLOSION
Durotan: Finally, it’s all over.
Hellscream: Gul’dan was defeated. Now, the horde is free again!
(Khadgar looks at Gul’dan’s staff)
Yrel: You think it is not over yet?
Khadgar: Gul’dan and his demon masters are not so easy to be defeated, I’m afraid this is only the beginning.
Yrel: We will help you whenever you need us.
Khadgar: So long till we meet again, look after yourself.
(then he flies away)
Yrel: A wise one used to tell me, the light will let us live forever. The future is ours. We will stand together and rebuild Draenor.
Really the point is that Grom doesn’t have a HEROIC SACRIFICE and basically everything ends like a TV episode