I feel like PvP content always lags behind PvE content by several years. PvP additions are always second fiddle to the story driven narrative based content. I think there could be a lot of merit both enjoyment wise on the player side and financially on the corporate side of committing an entire major patch cycle to new PvP content. Give all the WoW players some long lasting raid level polished content that they’ll be able to engage with for a long time coming. Compare how much use WSG has gotten compared to a big raid like ICC. WSG most certainly took way less effort to create than ICC but it has a much more active role in the player experience. The important thing to focus on would be making sure the purpose of the new content would be fun. Not some base form trite competitive team A fight team B over objective X experience. I know for a fact that there are bunch of creative people who could easily come up with awesome ideas on staff at blizzard.
As a corporate cherry on top you can do a big hype marketing campaign “BIGGEST PVP PATCH IN MMORPG HISTORY”