Warcraft IV confirmed!

[cmill78]

I have a feeling that we are going to lose one or two main lore characters early on in Legion. I also firmly believe Sylvanas will be involved in some story line that includes the Val'kir or maybe her sisters and possibly even Jaina Proudmore, as one of Sylvanas' sisters has small ties to Jaina. If, say, Thrall, Tirion and Sylvanas end up dead or taken out of commision, the time would be perfect to introduce new characters in a Warcraft 4 game once the dust has settled on the next expansion or three.

[Bioness]

or simply declare WoW (or the RTS game) non canon

That's just lazy, and would contradict everything up until now. Heroes of the Storm is only canon to itself for obvious reasons, but separating WoW and Warcraft makes no sense should another Warcraft game come.