wait what? what are you talking about?
this was confirmed in the recent Playstation magazine article
the factions and guilds you join will no longer exist in an isolated vacuum, but instead they will be affected by the events taking place in the larger world.
I take this to mean there is stronger likelihood of inter-faction blood feuds, maybe the College of Winterhold will ask you to burn down the Temple of Synod, for example, or some Necromancer base of power. If you choose to accept then you might not be able to join Synod, or be prevented from learning a new spell from the Necromancer faction.
At the very least there are going to be a lot of consequences for your choices relating to the civil war. Maybe The Companions are loyal to the Empire, and if you help the rebels they come after you, etc.