During BlizzCon '08 the Blizzard developers hosted a panel discussing current and future Player vs. Player changes and their logic behind them. Players packed into the crowded Hall C to find out what's coming up in arenas, battlegrounds, and what's going to be happening inside of Wintergrasp, World of Warcraft's all new outdoor PvP zone coming with Wrath of the Lich King.
The fire element was added as another dynamic element. Multiple fire hazards run the full length of the arena that fire at timed intervals causing players to have to adapt and make choices. They can either wait for the fire to subside to say get within range of another player or to hop on a pillar or they can walk through it which does a non-stackable DoT (10% for 3 ticks). They'll have to choose the damage or the setback of waiting. The damage can't stack so players will not get stuck in the fire.
BlizzCon 2008: WoW PvP Panel is the place to find out about all of the upcoming PvP changes.