Will Arena be active and competitive?

[Everenlol]

Or will people just continue to play on Blackrock for their arena fix?

[Radvo]

Pvp was active on old Lordaeron, but gradually decreased as the transfers were enabled (which won't happen here)

So yes. I think end-game PvP will be active. Actually no, I am certain.

[Tbcwascool]

I'm going Lord for PvP only, just like other people.

[Triggamix]

I am so excited for this realm.

[Rares13]

Or will people just continue to play on Blackrock for their arena fix?

Lordaeron will have around 4-5k players, which means that there can be a lot of teams battling for high rates even in 3v3 and why not 5v5,but it's only about player's mentality, because there will be the biggest pool of players, so numbers won't hinder the PvP. Since there will be so many players, once I'll reach a high level, I will form a 40man raid on weekly basis, to slay all the Horde leaders(to celebrate the fix of that quest that had been bugging Sylvanas) and give all the people mounts and achievements. Also, places such as Hillsbrad Foothills, Arathi Highlands will consist a point of attraction for all players who enjoy leveling and PvP-ing in the same time. Having 4-5k players online, means that every level bracket will give the players the chance to experiencing Arathi Basin(even at level 20-29), Eye of Storm, Strand of Ancients, Isle of Conquest and even Alterac Valley, before they hit level 80 .
In conclusion, Lordaeron is the most viable option for a true PvP player, who wants to experience the rest of the content as well, in an authentic way.

[Panofsky]

You should consider the fact we will face a gear progression sistem applied to one and only patch, the 3.3.5a. So, I suppose that since we will not reach the Relentless season the casters and rdps will dominate the ladder.