The 'let Blizzard be Blizzard' quote comes from the opinion and point of view of the Executive Producer and Vice President of World of Warcraft and their meetings with the folks from Bethesda and Mojang and comparing notes. It doesn't appear to be an official stance of Microsoft to not shake things up, but rather World of Warcraft itself is doing just fine that no one seems to want to intervene in its development.

“There’s no one asking us to do anything,” she continued. “World of Warcraft is doing very well and they’re very proud of what it’s been able to accomplish, so it’s almost like just let it be, and let it keep being awesome. They’ve been tremendously supportive and it’s like ‘let Blizzard be Blizzard’.”