This was discussed back in CBT2 and caused some "panic" aswell, luckily, beta testers and official response stepped calming us quite nicely.
Quote:
Originally Posted by Ayase
As jamein mentioned, this is just something that has been tested for the first zone of playing. It easily gets crowded when a lot of new players gets into the game at the same time upon release/beta, so adding a few different channels in these zones is a way to get to terms with the initial player rush. I'm sure that most would appreciate any efforts to make your first, few impressions of Aion smoother. It's not something that is considered for areas beyond that, and it does not change how servers work in any other way. Aion is still designed as a game taking place in one, singleton world*. 
* per server  |
Other than that, the world keeps being 90% seamless