Put the summary of the bug you're having here
I expected the world to load normally.
The world spawned in separated chunks
1. Load a world in 1.6.4, and don't move. Just stay where you spawned
2. Load up 14w11a, and go into the world.
3. Fly around and observe the environment.
This is to be expected and is normal and unavoidable. The world generation was changed in 1.7 so any chunks from before 1.7 will not line up with chunks from 1.7 or later. This is not a bug, simply the new world gen disagreeing with the old.