I am pretty sure the Protoss tried to curb the Zerg advancement by planetary exterminatus. It was at least mentioned in briefings, if not even shown in a cutscene.
I wonder if we'll get cutscenes to replace the explanatory text screens and briefings.
I'd be happy enough with remastered versions of the original cutscenes. 640x480 Smacker video looked decent in 1998, but it doesn't hold up today.