Blackrock Foundry was the second initial raid for WoD... so you're not wrong. WoD simply skipped the last raid tier entirely. I doubt Blizzard will repeat that. Blizzard made WoD only have three raid tiers because it was such a (relative) flop, and they foolishly thought that if they didn't work on a third patch that the next expansion would come out sooner.
It didn't work, so yeah... I can't imagine they'll try it again. It would just piss off players even further and increase the post-expansion downtime which is by far their lowest subscriber time. But who knows... Blizzard has made some incredibly foolish choices lately and this would match the kind of thinking they have lately. I don't think there's a much Blizzard can do anymore that would surprise me.