I think a lot of you are overestimating the Warcraft/Blizzard "fanbase." Yes, as far as computer games go, WoW is pretty big and a good number of people have at least heard of it. But top 200 movies of all time? I really, really doubt that. It does not even come close to comparing to, say, MCU like some people here seem to think it does. Besides, the advanced reviews coming out are pretty dismal, and that alone will probably turn a lot of people off from it - particularly people who aren't die-hard Warcraft fans.
Hell, I'm a day 1 WoW player, still playing to this day, and I probably won't go see it in theaters. Most people I know that play WoW are the same way.