With larger games, specially when talking MMO etc, there needs to be a way to manage / seperate players into seperate areas / shards (servers) etc. There is no way one game server can handle tens of thousands of players.

From current Esenthel design it seems a world is supposed to be hosted on a gameserver, and MMO's would have multiple gameservers. Therefore it makes sense to be able to render a neighboring world (within clients view distance). That way large battle areas can be built up and logically broken into seperate worlds / gameservers - each allowing a certain large number of players to be in battle with good performance. Naturally one won't be able to battle 'across' boundaries, but the scene design can take care of creating those breaks.