Just from a business side WoW does not look too interesting to host tournaments, especially as people are used to tournaments standards like SC2 has them. The money needed to make that work is a lot higher than the expected revenue.
With the new spectator mode it might be possible to do that but something like Hearthstone is just so much easier to set up and get decent viewer numbers with. It would take a massive effort and a big budget to make WoW tournaments work. The biggest factor in that is the community, there is very little hype around WoW tournaments. I spend my fair amount of time trying but after checking the numbers it would be so heavily dependant on external sponsorship that any organizer would have to do everything the sponsors ask for to pay the bills.
If Blizzard wants to create a tournament scene they need to invest heavily into organizations to build it up. Without financial backing I doubt there is a way to make it work.