Does this mean that to enjoy the PvP minigames that is promised, will you also need to belong to a guild that got a battle-keep?
No, but it means you will have to venture into the area to get to the NPCs who train PVP feats. The keeps are just a part of the pvp zones, and there will be multiple keeps in each area. The wider area in itself isnt ‘owned’ by anyone, just the key points, like the keeps, towers and resources are.