planning on merging the smallest of the US battlegroups. At present, Cataclysm contains 5 realms and Frenzy contains 7 -- while the next smallest battlegroup contains 12 realms and the rest of the battlegroups contain 15 to 20 realms. All in all this is probably good news for PvPers on the realms Shattered Halls, Azuremyst, The Underbog, Auchindoun, Coilfang, Blood Furnace, Terokkar, Exodar, Blade's Edge, Velen, Area 52, Zangarmarsh (hey, that's us!), and The Scryers, who should look forward to shorter battleground queues.
However, one thing this does tell me is that Blizzard isn't planning on adding new realms in the future -- or at least not a lot of them. These smaller battlegroups were obviously designed to give Blizzard room to grow, but the move to merge them suggests that Blizzard isn't planning on needing that room. As it was, to bring them to the size of the smallest existing battlegroup (the 12-realm Emberstorm), Cataclysm would need 7 more realms and Frenzy would need 5, for a total of 12 new realms. And to bring them up to size of the largest battlegroup, Cataclysm would need 15 additional realms and Frenzy would need 13, which would mean a total of 28 new realms. As it is, the merged Cataclysm/Frenzy battlegroup will contain 12 realms -- based on the size of the largest existing battlegroups, there's still room to grow, but it seems that Blizzard isn't planning on massive growth in the future.