I understand the intent of this code, but I'm a bit worried about adding backward compatibility code like this so early in development. Over time, this type of code becomes difficult to manage and maintain. 

Personally, I would be fine with just removing this block. If you feel strongly about keeping it, I think it would be best to file a code cleanup bug to remove this code after a sprint or two (this is making the assumption that most current Brackets users are updating every sprint or two, and would have already had there old prefs cleaned up).

Thoughts?