Bungie's community manager, Deej, has seemingly confirmed on Twitch (around 1hr49), that Destiny's planets will only have one area - or "destinations" as he calls them - each.
If this is accurate, that means that Old Russia, the area that we've already been exploring in the beta, is the only playable area on Earth that'll ship with the game in September. That would then mean that potential locations that have been previously mentioned, such as Old Chicago, might not be appearing in the full game when it's released in September, and may appear later as DLC, or in a sequel further down the line.