You don't know what rewards it will be, it could be rewards that are only usable in the Badlands, like bases and maybe a weapon that will be in your inventory when you're in the badlands or until you die, but cannot be used in the main world? They've said they will try to make it balanced and I trust that. If the rewards are too much they will notice it and I'm sure there will be a change to it.
You don't know that, we can't say that yet because we don't know what exactly we will get from the badlands yet. It won't be worth for an rp'er who likes rp more than pvp to go try their awful pvping skills trying to get something that isn't really worth anything in the mainland. And if it turns out to simply be a pvp zone, people won't be arsed to stay there for too long. If they get killed perhaps they decide to stay in the mainland for a while. A simple pvp-zone wont desolate Athera. However if they make the 'badlands' more than a pvp zone, with dungeons, good rewards etc, of course Athera will be desolated. But I don't think that's what they are aming for.
But also I hope there won't be anything too good as rewards for PvP, and have Dungeons and expeditions as a whole different thing from the PvP.