This is not a terribly surprising move. With the Cataclysm expansion focusing on the old world, the Blizzard developers no doubt want the old Azeroth to feel lived-in. As long as Dalaran (or Shattrath) has convenient portals to every old-world destination, players would continue to set their hearthstones there for ease of transportation.
However, transportation around the old world is not as limited as it was back in vanilla days. Some of the new zones like Deepholm have portals back to Stormwind and Orgrimmar; those capital cities themselves have portals to Deepholm and others that are not yet active. We've also seen signs of new portals being constructed in the Twilight Highlands.
World of Warcraft: Cataclysm will destroy Azeroth as we know it; nothing will be the same! In WoW Insider's Guide to Cataclysm, you can find out everything you need to know about WoW's third expansion, from brand new races to revamped quests and zones. Visit our Cataclysm news category for the most recent posts having to do with the Cataclysm expansion.