New Realms
Another solution would be to open new realms. Nowadays, a World of Warcraft realm isn’t limited by hardware as it would have been in the past. We could open one or five or ten new realms in each region if we believed that players would move to them from the overpopulated realms. However, the data we have suggests that wouldn’t happen.
In part, that’s because there’s sufficient space on the currently existing realms for all of the players who want to play. The social bonds that players make in game causes them to stick with the realm they’re on. We don’t believe that making more realms available would change that.