The problem is that they seem hell-bent on changing the Realms so that it conforms to everything 4e is doing and introducing:
The 4e standard cosmology changes, and the Realms' cosmology changes (with its own RBE "explaining" that change) so it's just like the 4e standard cosmology.
4e is apparently all about "Points of Light" so the Realms need big catastrophy and many cities destroyed so the Realms scream POINTS OF LIGHT.
4e magic works differently, and they kill off deities to explain why Realms Magic now works differently (which also means that you couldn't play "historical" campaigns properly with 4e rules, since they would play in a time when wizards didn't have arcane strikes).
They don't have to write sourcebooks for the standard campaign setting, because the Realms are just like that, so they just release FR books.