The closest thing to an official statement is a tweet by Micky Neilson (who was at the time publishing lead and senior writer of Blizzard):
Zerde3: @MickyNeilson Will the Warcraft movie become "canon" lore, or is it like a parallel universe like WoD? except no interaction between the two
MickyNeilson: @Zerde3 Separate.
Based on this, I feel it's fairly safe to say that the movie officially exists in its own canon, as Radhil suggested.
