When it was unveiled, Nintendo said the 3DS's design wasn't final and would change prior before it's launch, similar to the original DS. Well, that was more of gamers bitching up and down Main Street about it's godawful design, so Nintendo changed it to the much more appealing - yet archaic by today's standards - design that we see today.
Now, Nintendo went back on their word and said the 3DS's design will remain mostly unchanged, saying "You can take this as the final shape".
They could do minor tweaks here and there, but what you see is pretty much what you'll get when the thing comes out. Whenever that is.