I wouldn't worry much about performance in your case. Just make the chunks small enough, and there won't even be a dent in the FPS when a new chunk is loaded. Try to aim for 16x16 chunks.
Thanks for your answer! Well, making the chunks small enough does work for this project, since I'm using a heightmap, but for my 3D-Cube-World, it lags the game down once in a while. What I'll try now is doing the loading in the free time between the render loop and the next execution of it.