Not only is bringing back vanilla wow not guaranteed to be profitable enough to be worth the effort and resources, but there's the issue of is there any interest in it? Would any of their devs be excited and passionate about bringing it back? Is it something anyone there WANTS to do creatively?
Also you can add StarCraft Ghost to the list, I'm not sure if it was as far along as Warcraft Adventures but it saw a lot of development time, and even had a novel written that was meant to accompany it.
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What met their standards 12 years ago may not meet their standards today with over a decade of experience developing said MMO from what it was to what it is.